Can't really think anything since there are no specifics.
Before you get irate with him or anything else, try to see if they will tell you what they are gonna do. If you were REALLY concerened about your trans, you would've done that before hand.
If they put a shift kit in it(doesn't need it for street use) and they don't upgrade some of the hard parts in it, it will actually make the trans MORE prone to break. Especially the sun gear shell.
Ask them exactly what they put it in.
See if they will give you a list of part numbers (they've gotta order them and will have them) and who's shift kit they put in it.
A "shift kit" is a generic term. We can make syty's shift harder with a couple springs, blocked accumulator, a piston, an 1/8" rod to block one of the valves in the valvebody, a TV boost valve and a reverse boost valve. Cost about $25 for all the stuff.
I can see you researched this :roll:
Guys will ask 1000 questions on a boost controller but go get the cheapest trans they can.....and then gripe when it breaks
Off my soapbox now.
I suggest to guys that they get the number off the edge of the trans on the passenger side along the pan sealing surface of the tranny and write that number down. Then check it when you get your ride back. That way you know right off the bat if its gonna shift like an ice cream truck or not.