Rear Transmission Bearing

Highly unlikely, although I am infamiliar with the exact transmission you have. That part that looks like it could be removed is called an extention housing. It generally contains the extention shaft, speed sensor, and rear seal. The rear bearing is further up in the transmission. And on top of that, most automatic transmissions are rebuilt by removing the bell housing in front, and the valve body on bottom to gain access to the inards. Replacing that rear bearing is one of the first steps in putting it all back together after an overhaul.

If you mean the rear seal because of leaking fluid at the drive shaft, that is possible. Just remove the drive shaft from the rear axle making sure to mark orientation, and slide it out if the tranny. Use a screwdriver or punch to VERY CAREFULLY get the old seal out, and use a socket or seal driver to drive the new one in.