We want to buy a fiberglass tub with the surround , but not sure on how to get it in. The hall and a tight turn may be an issue.

If it's cast iron, which is looks like it is, it can be broken with a sledge hammer. I think they break pretty cleanly, but I'd wear eye protection and cover up anything else breakable.

You can also refinish cast iron bath tubs, but I suspect that one's too far gone and doesn't have a style worth preserving.

If you want to replace it, order the new one first to make sure you have it on hand, then start on deconstruction. Remove the tub surround first. See how much of the plumbing needs replacement. Then remove the tub. There will be some wall damage. Take the bathroom door off its hinges to give you more clearance. You may also have to remove the toilet to get the tub out.

If it is a cast iron tub, it will take several strong people to remove. If it is porcelain over steel, it will not be nearly so heavy.

The real problem, it's our only bathroom. The house was built in the early '60's and I'm sure it's original.
Once we remove the wall surround , if there is damage what type of wall board should be used? We live in Texas

There is another reason to look into a professional restoration done on-site: cast iron holds heat in, making bathing a pleasant experience. The newer fiberglass tub will not, making bathing a quick experience. You can expect an additional 15-20 years on average from a new finish.

Tub can be removed turn water off l it also has a cheap plastic insert that will come out easy. Google how to remove old bath tub. You can DYI, but will need help. Do you want a tub? You could just add a very big shower. Tile, get help on that. Travertine is always nice. Tile in bath room needs a moister board behind it. Let a pro do it. That tub is disgusting.

The comparatively sharp edges on the top make it look a lot more like porcelain over steel than cast iron. Can you crawl under the house to see what is what? Also look at a few of these articles listed on the side of this website, FWIW: http://www.ehow.com/how_8454094_identify-old-castiron-steel-tub.html

If this tub is in the house there must have been room for it to have fitted on its way in and still fit on its way out, unless you have modified the hallway etc...

Tubs can fit though doors not that wide, just heavy.

Use cement board on walls once tub and existing walls are removed. Fiberglass tub and surround come in sections for remodel purposes where space is limited to get unit in. The one piece surround unit are for new build homes.
A contractor can usually get you a functional (if not completely finished) tub in a day or two but a DYI might take longer.
If you have a gym membership you might be able to shower there or you'll need to run to a family members home for a few days.

@Travisinteriors, not very tactful, I'm sure they know the tub is in rough condtion and that is the reason they are looking to change it. No need to call it disgusting.

Remove the doors and get extra men power ,I know that they are heavy:( we had one removed . But these are the best ,they keep the water warm longer then any other modern made tubs. If you could get it re-glazed ,it probably be worth it . It doesn't look too good from what I can see on the picture ,but a professional can fix it up for you.

It appears a fiberglass surround was added after original build. The original walls might have been tile that was not in good condition, so they placed a surround on walls and left the tub.

American Standard makes a tub that is similar to cast iron but is not nearly as heavy and it keeps the water hotter longer because it is insulated...(Americast is what they call it) they come in the standard sizes, 60x30 and 60x32...for the walls I would suggest either tiling them or using Swanstone (which is a solid surface material) a sledge hammer will make quick work of the old tub :)