Check for an alphanumeric code on the side of the cartridge, on the seals, reading something like "SKF 6002" or such. This'll indicate the replacement bearing, and most cartridge bearings are easily purchased (try bocabearing.com, for one).
Installation, though, isn't quite so simple. (Even my old Sutherland's manual doesn't offer much help on the topic.) Some cartridge bearings were press-fitted into the hub shell rather loosely, and practically fall out with little encouragement. Others were pressed much tighter, and/or glued in to boot; for these you'd need a bearing-pulling tool of some sort. I've had mixed results with these. Then, once you pop the old bearings out, so the theory goes, you just pop the new ones in their place, and reassemble. The trouble is that the new bearings don't want to fit into their new home any more than the old ones wanted to leave. Plus, with the cartridge bearing, getting the bearing seated in the hub shell is critical, and there's nothing as frustrating as having to remove the recalcitrant bearing again and again because the damned thing just won't sit right.
My advice is if you're mechanically inclined, you could give it a go, or just find a shop where the repair guys are a little older. This was a popular enough hub that, unless you live in the sticks, some shop around you will have had experience with, and be able to help.
