If your transmission is indeed shot, and you plan to swap it out rather than repair it, then I recommend finishing it off. You know, pour salt water down its gullet and then do burnouts on the rev limiter, or find out how fast you can go while slamming it into park without breaking the trans. Oooooo - crank it up to 5K on the tach and then put it into reverse with the brake peddle to the floor. Maybe drain the trans fluid (by shooting a hole in the pan) and then floor it in D and see how long it takes for smoke to come out of the filler tube. Try not to break other parts of course, but generally speaking, the trans is the weak link (with any luck).
Its like when I scrap a rig. By the time I'm done with the car, the scrapper can not stop laughing his ass off while he was winching (what is left of the car) up onto the tow truck.
If its going out, let it go out in style.
Obviously with any transmission failure, you want to flush the cooler lines, and replace the tranny cooler. Aftermarket coolers are cheap and easy to install.