You're going to have to get that thing up pretty high to slip the tranny under. Most people use jack stands, but I prefer to use cribs...a lot safer!
I've always pulled the engine when I've had to swap out the tranny so I can't give you specific guidance in doing it from underneath. You'll probably have to pull the driveshaft so a couple of large crescent wrenches or pliers to separate the two halves if you separate it. A transmission jack might be nice to have or help to balance it on a floor jack while lifting it in place. Make sure you get the torque converter fully seated or you'll damage the trans. Check the flex disk and trans mount while you're under there. Might also be a good time to replace the exhaust donuts while under there.
Good luck with the project and be safe.