Has anyone replaced this part before? I need to replace my tail shaft seal because it is leaking, and I think that this bushing might be worn out as well since the two are connected. Do you know where the hell I could order one of these from, seeing as how the local Mazda dealership basically had no idea what an RX-7 was? Would Malloy be able to find this part?

 

Before you order the bearing, put it up on jackstands, go under & wiggle the front end of the drive shaft.
You'll be able to feel if the bearing is bad.

And - yes it can be replaced fron underneith.
Unbolt & remove the Y-pipe.
Unbolt the dive shaft flange at the differential & slide it out.
Pull the seal.
You will need to rent, borrow or make a puller to get it out.