I have rebuilt them without ever getting the "cup" (as I call it) out of the rear end. So unless you are going to change it entirely, I say rebuild it in place. Getting the ends out of the differentials is the hardest job I have come across yet.
If you really need to get it out... soak with PB blaster for a few days, clamp some vise grips on it after wedging a pry bars behind it. Pull the vice grips while forcefully prying, with a second pry bar on the opposite side from the first pry bar. The idea is to get tension on the joint with the first pry bar, then a sudden force on the other side to finish popping it out (it also helps to ensure it is coming out straight and therefore not binding itself.)
If that wont do it, I have had to pull the other side out and drive it our from the opposite side.
As far as whether it is too worn, I can't say. Even photos wouldn't help with that. Without getting hands on it, and feeling how it moves, and if it has any burrs, I can't say. You could try putting it back together with the same race and bearings and seeing how freely it moves. If, after that, you feel like it is just going to fall apart again, I probably would get a new one.
MINE:2015 Sportsman SP 850 Sunset Red
Back seat / cargo box and footpegs from Thor, Polaris 2500 Winch with synthetic rope, Polaris front and back bumpers, Polaris Lock-n-Ride Mid windsheild, Heated handgrips, Fender Flares, Rotax 2+2 Fuel Cans on front rack.
HERS:2015 Sportsman SP 850 Touring Sunset Red
Polaris 2500 Winch with synthetic rope, Polaris front and back bumpers, Polaris Lock-n-Ride Mid windsheild, Heated handgrips, Fender Flares
RIP Sarge (2004 Sportsman 700 EFI killed on trail 32, Rock House, Hatfield-McCoy)
Last edited by KICKER431; 11-05-2013 at 10:04 AM.