Transmission Problems

Hey, I got an 89 Firebird with a 350 and 700R4 trans. The problem i'm having is that my radiator went out and mixed a bunch of water in with my transmission. So I changed the filter and flushed the fluid, now when it shifts it goes through 1st and 2nd and instead of going into 3rd it shifts back into 1st. If I do end up needing a complete rebuild how hard would this trans be to rebuild? Also would I need like any special tools or anything?

Since it's an auto..sorry to say but might be TOTALLY easier to just take it to a mechanic and let those dudes mess with it, to save a lot of money, take out the trans yourself, then when you get it back, put it back in yourself.