To remove the transmission:
Just disconnect the torque tube at the u-joint and lift it up out of the way using a floor jack (or by hand, if you have the strength). Hold up the tube with a a 2x4 board that is cut to fit side-to-side inside the frame rails. Or, let the torque tube drop to the ground (it is in your way there, but not in the way of removing the transmission). Moving and holding the torque tube up is the better option.
I have done this with the rear of the truck on the ground and on stands (on stands, you have less resistance and more space to move around under the truck). Place the stands under parts that do not need to rotate. Last summer, I easily did this to remove an engine from a truck with a 3-speed and from another truck with a four speed.
Removing the transmission. 
