Hi Orion,
My TH350 is also on the way out. In mine, reverse doesn't work, and for right now it's my daily driver (tactical parking, anyone???)
Anyway, I called my local shops and no one would rebuild it for less than $800 -- then I started looking around and I found a couple of different auto parts stores that carry rebuilt TH350s. The warranties are still in the 18-24 month range, but the prices were around $400-450.
Now I know the quality isn't going to be the same with one of these as it would be with a Delco rebuild, but I'd rather take my chances if I can get about the same warranty for 1/3 the price. And I'd rather not have a local shop rebuild my tranny for twice the cost of replacing it. So I'm going to take one of these weekends and swap out my tranny with a rebuilt one.
Just my $.02
-John