You only need to replace the rear bearing.
http://www.pspec.com/details.asp?ProdID=77&category=7
Here's the link to performance specialties. Look under accesories.

The front bearing is pretty safe, I've only had one go bad after a mid air.

To change the bearing you need to dis-assemble the whole engine, use a little heat from a propane torch and bang it down on a bench it will fall right out. I'm sure there are plenty of threads here in RCU about how to replace bearings, it's pretty simple.

Be sure to inspect your piston and sleeve for scratches. Also pay attention to which way the piston and rod assembly face when you take the engine apart. I know my .40s will only fit one way but can't remember the .46 it was a year or more ago.