Chances of finding a small issue that can be fixed without a rebuild are slim.
How much does trans fluid cost? How many times you going to fill and drain and throw away that fluid before rebuilding anyway? How much time, labor, and smelling of trans fluid before having to break down and rebuild? Even if just one band or adjustment makes it work again, how long before it finally burns up complete? Hint: less time than if it was overhauled. Next time you may not be so close to home..
The kits are cheap and you'll score a converter one way or another. Tear into it with lots of pictures and a FSM on hand. It's really not hard and you'll learn a ton along the way... Just my $.02