7b, clay soil, sounds familiar. Where are you located?

I will be getting a soil test for sure first.

A soil test is good but nutrient levels take time to change, so no rush on that, nothing is going to change before seeding time.

I learned that the pre-em doesnt do well in the thin grass, which seems to explain why I got so much crab grass.

That's false, pre-emergent, when applied properly, will work on bare dirt , mulched areas etc.

1) I need to kill off the crabgrass.

If you have less than 50% grass just use glyphosate.

2) Top dress (?) Would a good quality topsoil be a wise thing to topdress with? Is that more dependent on what the soil test says?

No need to topdress at all.

4) Seed. Is slit seeding superior to broadcast? Ive never used it beforer

If area is prepared properly broadcast works just fine.

The yard has decent slope, would slit seeding help reduce any potential runoff if a heavy rain occurs? What are the best ways to help prevent any runoff?

Slit seeding will definitely help in that case.

5) Pre-emergent. I have Tenacity which I have not used yet. My understanding is an application at the time of fall seeding will help prevent winder weeds, including poa annua which Ive had problems with in the past.

That is false, Tenacity only lasts about 30 days, and it's pre-emergent effect on poa annua is slim to none. It does help with many other weeds. You will need to apply something like prodiamine to take you through the winter.

6) Starter fertilize. I have been using milorganite since the spring. 2 applications so far and one more about to come up. However, should I use the milorganite now if I plan to be using a starter fertilizer when I seed or wait?

I would wait, you don't want your existing grass growing too fast at the time of seeding.

7) Winder fertilize. Would this be the time for the next round of Milorganite ? (post germination fertilization is something I did not do last year... maybe that accounts for the thin spring?)

Yes, failure to properly fertilize will result in a thin stand. Forget the MIlorganite. Besides the starter you will need 3 additional rounds of fertilizer at bag rate this fall, October, November and last one in December(winterizer) which should be straight urea. Any non-organic lawn fertilizer will do. If you want to do organics start next year, a new stand of grass should be fed with synthetics.

8) Come spring, is it best to control weeds through the summer, which was my plan this year,

Be ready to apply prodiamine at 5 month rate March 1st. Miss that one and you'll be in the weeds, literally. Stay on top of the weeds throughout summer.

or thicken up the yard even more by overseeding (if needed) and let the density of the lawn do most of the weed control

Total myth - crabgrass, bermuda, virginia buttonweed will poke through the thickest lawn and take over in the summer. Pre-emergent is key, followed by strict post-emergent control for whatever breaks through.

Please help! Let me know your thoughts on the steps above, what you might change and how I can help ensure a better renovation this time around.

Here's some additional info on the overseeding process.

http://lawniac.com/overseeding-fescue-lawns

Thanks for the detailed reply.

I am in the Raleigh, NC area.

A few follow up questions.

Regarding tenacity, when it is best used? More for spot treating specific weeds rather than as a broad spectrum?

Can the prodiamine be used in fall during seeding time as well as spring for crabgrass control?

You mention a heavy fertilizer schedule after seeding, which I did NOT follow last year... would each subsequent fertilization be anything specific or more starter?

Regarding tenacity, when it is best used? More for spot treating specific weeds rather than as a broad spectrum?

I think its best use is for pre-emergent control during seeding. It has a few specific uses for post-emergent control as well, but for most other weeds there's other options.

Can the prodiamine be used in fall during seeding time as well as spring for crabgrass control?

You cannot spray prodiamine during seeding time, it stops all seeds from germinating, including the grass. Use Tenacity during seeding and move to prodiamine after the grass has established for long term winter weed control. Then apply prodiamine again in the spring for crabgrass etc.

would each subsequent fertilization be anything specific or more starter?

Unless your soil test shows a phosphorus deficiency, you shouldn't use more starter. Any lawn fertilizer will do - say Lesco 24-0-11. The target is one pound of nitrogen per app, so in this example - the Lesco 24-0-11 - you would put down ~4 pounds of fertilizer per thousand square feet each application.

Regardless of your preM product of choice, the key is to stay consistent with your app timing to build a barrier in the soil. It doesn't just zap this year's Crabgrass crop, then go away so you can reseed--Although we all wish it worked like that!

It took me 3 years of quarterly preM applications, combined with monthly spot spray sessions each summer to get Crabgrass free & I still get 6 or 8 individual plants that pop up each year. Stay vigilant & consistent, don't get discouraged.

You might also look into a higher quality seed--In addition to your existing Crabgrass seeds in the soil, chances are good that lesco seed brought in orchard grass, which looks a lot like Crabgrass.