Most of the time with components including stock band, corvette Servo, servo cover they don’t need shims, but it’s always best practise to check anyway. The instructions that come with the shift kit will tell you how to shim the servo if required.
Only thing you’d need to pull the trans apart for is the apply piston springs - and that’s optional and only really absolutely necessary for transmissions operating at 6000rpm+.
Tbh, again I don’t think it’s worth spending your money on for a v6 especially if you need to pay somebody to do it for you. If it were a demanding engine like an ls1 with some work done and it had its work cut out for it, I’d definitely kit it properly (like I did with mine). Throw a good second hand trans in if it starts to give up. They’re cheap enough.
The kits can be fitted whilst in the car. May need to drop y piece to gain access to pan.