2000 A6 quattro Avant. Rear wheel bearing
 

I have a 2000 A6 Quattro Avant. The passenger rear wheel is locked up. I was told it is the wheel bearing. Can anyone tell me how hard it is to change out? And is it possible that the bearing is the cause of my problem??? Any help would be greatly appreciated

It could be a bearing - if so you'll need a press to change it. Try dismounting the caliper from the hub. If you can, then a bearing is likely. If you can't get the caliper off, the caliper is seized or the e-brake mechanism is stuck and you'll need a caliper (happened to both rears on my A4).