Free: Contests & Raffles.
Depending on the year I'd be fairly 99.9% confident you're going to need more than just a flash. Flash/reflash == software update. You'd likely need the ECM that fits the vehicle that the transmission comes out of along with wiring harnesses for speed sensors, neutral safety switch, etc.
I hate the internet!!! I am getting mixed answers on whether or not flashing fixes the problems or not. Coach, this is all just hypothetical, my bud has a transmission that he is willing to sell for cheap. The only down side is the electrical side of it. But I still think I am gonna do it.