Overall appearance will tell you a little about it.........does it look dry or is it oil stained (leaks). Looking at the fluid can tell you a lot too. At the minimum I would change the filter and pan gasket, as well as the front seal and the little seal that goes around the shift shaft. It is SO much easier to do those now with it sitting on the floor.

If you have a good , honest transmission shop in town I would spend a hundred bucks or so and let then change those things. TH350's are a good transmisson and not overly expensive to have those things changed on. Just a thought.

Don