I'd find the tranny model number then google it for problems. GM FWD trannies are terrible!
It can cost you $$$$$$$.
But if you still want one, get a shop to scan the tranny and printout all data.
Any values above default in the “Transmission PCM Steady State TAP data” shows there's a near future
problem, bargain for a lower price, ie - $1,500 or so.