You know I haven't checked the installation procedure yet, but as far as I know the bearings are not greased, they are lubed by the diff oil in the rear axle tube. If your grease is actually gear oil mixed with dirt it may be that it is only the oil seal that has failed (possibly due to blocked breather causing axle to pressurize). If so you will need to remove the half shafts and take the bearings off to get to the seals (Aqua Puttana did a pretty good write up on this in the T1N section).
First though I would check carefully and see if someone has just selectively greased the contact points between the shoes and the backplate - I normally use a little smear of copper grease for this but maybe someone used some other kind of grease?