How many miles on the car. Do you know anything about the car's history? An oil and filter change, or better yet a flush, is the only thing you can do to the tranny and is the first thing I do to any used car that I buy along with plugs, wires, belts and hoses and coolant. A brake inspection is also a good thing to do.
You can have the TCM scanned at the dealer for a fee. Will tell you if any fault codes are stored in the TCM along with the CVI's which are good to know because they indicate the amount of clutch wear. Just my $0.02.