Chevrolet Repair: tcc switch, craddle, old salt

Question
I have a 1994 caddie. sts. Northstar enging. Im going to swap the engine tans and craddle all at once.  the new assemebly I got has 80,000 on it.  he said it runs great but right before he pulled the assembly out. the trans started to kick out of overdrive.  He said some days it would happen all the time and some days only once in a while. He said that the engine light came on at the same time when this started to happen.  They scanned it with a snapon dig.  and said it was a TCC swith, Transmisson control swith.  Heres the problem.  He said you can only get to that switch with the trans out because of the pan clearence.  Im not sure if I should take the chance and replace that switch and put the new unit in or split the engines and trans, and use my 175000 mile old trans that was ok.  Thanks for the time and help.  Im stress alittle bit on this one because this will be a big job for me.  No hoist, doing this one on the back.  Thnanks./

Answer
I was with you up to the point you said "No hoist, doing this one on the back."
Expect great stress in this challenge.
Hint: (I have tried replacing the same motor in the back of someone elses yard,long story) call a wrecker/sling truck to hoist it in!! $35 bucks for service call,$0 for AAA.
Call me an old salt, but I would change the transmission pending everythings the same and your trans had no problems. Just take care of that old trans by changing fluid often.