I'd suggest going on ebay and doing a search for "4T65E TransGo". Buy one.
Go to your GM dealer and buy a tranmission filter. Buy 8 quarts (IIRC 8 is correct, but it could vary from car to car) of the proper transmission fluid for our cars.
Then have the mechanic that swaps your motor put the new filter and shift kit in. Use the medium firm shift and you should be golden for some time to come.
If you buy the new aluminum frame LIM gasket from GM it will only cost you around $45 and it shouldn't take the shop 1 hr to change with the motor out of the car prior to installation.