Depends on the type of bearing and where it's used.
Usually, it'll be more acurate to talk about replace than repair.
For something like a car, a wheel bearing consists of:
- inner race
- rollers or balls
- outer race
The inner race is pressed onto an axle, the outer race is pressed into a hub, and the rollers/balls go inbetween them. To replace, you pull the inner race off the axle and the outer race out of the hub. Press on/in the new parts and you're done. The above is simplified, but the exact procedure varies from vehicle to vehicle, so I couldn't give it to you anyhow.
