Hey Nate don't you work at a Tranny Shop?
As for a replacement I would suggest the following...
1) local shop, nice if there is ever a problem
2) somone like
www.maddogtransmissions.com he seems to be really cool and I have only heard great things about him
3) Factory GM replacement through your local dealer
4) find a 2nd generation 700r4 and have the local shop rebuild it
That is the list that I have come to like from my searches regarding this very topic as my 700r4 is also on its last leg.
Mine doesn't like to shift out of first either, just get into the throttle then when it racks up enough rpm's just let up on the peddle and it'll shift into 2nd then be sure to roll back into it so you don't slow down too much and bogg down the engine.
Sounds dumb but it works, I've been doing that for over 6 months at about 20 miles a day for work and school. Oh that and Lucas Oil Transmisison stop slip helped me.
-Avery