You can and should replace it--it'll look silly with big floor moulding and skinny door casings. The big plain stuff like in your inspiration picture is pretty easy to do and it'll look good with your high ceilings.

(And if you ding your wall ripping it out, it'll be covered with the new stuff!)

Thanks fori and worthy. I asked here before I even thought to Google...I found some videos on YouTube. One guy popped off the existing casing quite easily; it looked like only a couple tiny brads held them on. Another guy spent some time cutting/digging out the caulk, but thankfully mine aren't caulked. I'm hoping not to damage the existing door frame or door paint, and to paint just the new casing to match the existing door and frame.

I'm thinking 6" baseboards and 4" door casings. In the inspiration pic I posted, the baseboards looks about 6" to me, and the large doorway in the foreground has the same size casings, but the smaller French door in the background has a narrower casing I'm guessing is about 4". Sounds like 4" is a standard casing size. Anyone have opinions about these proportions?

If you have "split jamb" prehung doors, it's very problematic to remove and replace the casings, because the jambs are made in two pieces and may not have been properly shimmed and nailed to framing. Split jamb doors are favored for tract houses where speed of installation trumps all other considerations; you can hang one in 10 minutes, do a whole house in a morning.
If you can pry off the door stops, you have conventional jambs;' if the doorstop is integral to the jambs, in your case they are probably prehung.
The casing will be applied with glue and staples, and some prep work will be required to clean up the edges. Also, the jambs themselves may start to come apart, because the glued/stapled trim was helping to hold it all together.
Once you get the casing off, you can add more shims and nails to firm up the jambs as needed.
Casey

Good reminder!
I 've never even installed pre-hungs, let alone split-jamb pre-hungs.

Hmm...yeah, I'll bet that's what I have. This is definitely a tract house. I Google-image-searched split-jamb prehung, and some of those images look just like my doors. I found a FIne Homebuilding article about installing them.

There's so many cases in this tract house, where the building method designed to be fast/easy/cheap makes it soooooo hard to replace/improve/repair later on.

Well, my contractor (a retired friend who is helping/advising me, but I'm doing as much work as I can) said he'd never heard of split-jambs out here in CA. BUT, I just tore one casing off the least conspicuous door in the house, the back stairway leading to the garage, to see if it would be feasible. It was hard to get off, and it took maybe 30-45 minutes. This was just for ONE side of the door. It had a lot of staples, and a LOT of really long nails (about 2.5") holding this light, small piece of the wood in place. I made progress much faster once I learned to set the chisel on the inside of the jamb, rather than outside by the wall. The many layers of oil-based paint really bond that casing to the wall and to the mud inside the jamb. The bond is actually stronger than the wood itself at times; the wood split apart, while the oil-based paint gripped tightly to the wall and the jamb.

Oh well. I have plenty of time and patience, so since it does seem possible, I will tear them off. If anyone has any helpful hints, I'm all ears. I've considered whether my oscillating multi-tool would be helpful to cut through the paint from the wall side of the casing.

Well what type of jambs do you have, split or one piece? Also you could probably cut along the casing/sheetrock line with a sharp utility knife to cut thru that paint

Maybe split jambs are an east coast thing. Here if you buy a prehung door off the shelf at HD or Lowe's, it's a split with 2 1/4" colonial casing.
Casey

Maybe worse than split jambs, he's following the trail of a diyer convinced that long nails are the cure for everything. I took apart one house where even ceiling tiles were nailed on that way. And all those coats of paint in a 20 year old building. Sounds like it was a rental at one time.

OK, I'm a bit late to the party, but an alternative to replacing all the casings would be to cut off some of the bottom with a Dremel and put in thick, rectangular plinth blocks at the base, for the baseboard to butt into.

But if you want to widen the casings as well as solve the skinny-at-the-baseboard issue, then you can go ahead and rip 'em all out. That's what I did in our house (about 30 doors total).

Hey Andersons - I see you are considering an oscillating saw. We bought a Rigid brand one & have used it for a few jobs. It isn't fast, but it is pretty handy.

Have you decided what to do for the moldings? We are looking for a similar style & our contractor says he'd use 5/4" material for the piece that goes across the top of the doorway & 3/4" material for the pieces on the sides. There is another style that has a filet and crown around the top, but I like the simpler look like what you posted.

Good luck with your project!
-EChic

millworkman, I still don't know if they're split or not. The test of how easy it is to budge the door stop, I'm not going to do, because I don't want to replace anything else about the doors, or even repaint them. The split-jamb casings are supposedly attached with lots of staples at the factory, and these certainly do have the staples.

I did cut through the paint at the casing/sheetrock line, as well as the casing/jamb, but that didn't always help...because when the chisel applied force to pry the pieces apart, it didn't always apply force where I scored the paint. In those cases, the alkyd paint pulled off some of the wall paint in the surrounding area, even though I had scored it where I thought the joint was (under all that paint).

I do know that no DIYers or renters were ever here...this workmanship was done by the builder. The builder is long out of business, built a bunch of homes and condos for our community in SoCal. A friend did put a bunch of coats of this alkyd paint on the doors and casings about 10 years later.

weedyacres, I did consider cutting out the bottom and putting in a plinth. I also considered building up the width and depth by adding another piece on the outside of all the casing. But, I just think that a larger, flat, plain casing is the look I'm going for. So I'm gonna rip 'em all out, as I redo the flooring in each room.

EngineerChic, I have a cheapie Harbor Freight multi-tool I haven't used yet, but I've been watching videos on what the different blades will do, and I think it will come in handy for my remodel. I've never done more than tap in a picture nail before this.

That is really thick stock your contractor is suggesting! I was thinking 1/2" or so for base, 5/8" for casing so it's a little deeper than the base. I need some samples to see if this looks good. It seems to be hard to find this plain style of molding around here. I found a 5.5" high base that's only slightly rounded on the edge (do NOT want bullnose), but I haven't found any casing that's about 4" wide and a little more than 1/2" thick...