Jim Barrett did an article about this in a long ago issue of OGR. Maybe he could chime in on this one and give you the straight scoop.
If I remember correctly there was a main article and then some further small updates, so, you may want to get them all before ordering any parts. I think the big thing was, catching the problem before it had severely messed up the running gear. If you can catch it quick, it is not too hard to replace the bearings. But, if you have run it enough to where the gear on the axle has been damaged, then you should send it to a pro.