While bearings can be replaced and rebuilt, it is generally easier for the DIY mechanic to replace the entire hub assembly. Especially on a FWD car, the rear hub is only held on by a few bolts. For detailed instructions, please read my recent articles on FCPEuro about How to Replace Rear Hub/Wheel Bearings on a FWD P1 Volvo.
You can also watch my how-to video here: