I know that some 01's and maybe some early 02's had bad seals on the front bearings allowing water in resulting in rust of the rollers and races. You can replace the bearing inside the "knuckle" on the front, or do what MMC does and replace the whole thing. Can't remember the price of the bearing itself, but I priced the whole unit at about $225 a side for the fronts.

As for the rear, I really haven't heard of anyone having issues out of them. I have 146,000mi on my 01 Limited and it's doing worderful bearing-wise.

I think there is a tech thread on front bearing replace ment of the Gen III on here somewhere.