replacing rear wheel bearings is a normal cost of ownership. here are the parts:
28016PA010 roller bearing
28015AA070 oil seal
28015AA021 oil seal
28044AA000 axle nut
these parts cost a little over $100 and the dealer has usually charged four hours labor.
the last time i got mine done at a private shop and they removed the housing, then the hub using a hub stand in a vise. they suggested that some dealers might be trying to do the job with the hub still on the car using a BFH (in the vernacular), which is not the way to ensure a long-term repair.
AllData has a good write up on this if your mechanic has a subscription to it.
HTH
