Removing and re-installing the 3 speed transmission is much easier if you remove the cross member at the rear of the transmission. There are about 12 bolts holding this cross member to the sides of the frame. This is the cross member that the rear transmission support mounts to. In fact, I could not figure out how to re-install the rear transmission support with the cross member in place. Also, as Tim suggests be sure to use the guide supports at the top of the transmission when pulling the transmission. If you don't it's easy to either damage the springs on the pressure plate or cause the clutch to become mis-aligned. I just went through this a couple of months ago and you almost need a second set of hands to wiggle and turn the throw-out bearing onto the snout of the transmission and you are guiding the transmission into position.
Mike