If it is a pre-94 oval inlet blower don't spend much money on it. if it is 94-95 supercharger with rectangular inlet you can talk to this guy... http://www.magnumpowers.com/ lots of options .. Depending on your budget he has options including porting rotor coating along with rebuild, complete hi perf cases etc. If you have access to a 12-ton or more press you can change snout and rear bearings. The rotor bearings are best left to pros..
you can replace the snout bearings but you'll need a hydraulic press. You can get one at Harbor Freight for about $120-$150...There are also youtube videos floating around on how do it...just search M90 rebuild. I think the one I saw was for a Grand Prix but should be same exact process. Better yet post something in Parts Wanted and get a good working snout or even a whole late model blower.
Rebuilds vary but most are just the snout bearings and rear case bearings and fresh oil. If you go with magnum I believe he has a rotor plate that is rebuildable..chnging the rotor plate bearings is a risky proposition...your risk messing up rotor timing as well as wrecking a lip that kind of holds the bearing in place. Most people leave it alone. For the money you'll be spending you're better off keeping an eye out for a good used late model that someone already rebuilt. The big shoot out just came to a close and Id bet money some of those guys are thinking of going bigger and faster next yr...ditching freshly built ported late models for mpx and beyond. Two big sale times on this forum...just before the shootout and right after for winter build. Good luck!
You can rebuild your early model yourself if you have some moderate mechanical abilities. A press could be used, but is not necessary. I rebuilt mine about 7 years ago using the freezer + oven method (heat parts and cool parts at the same time, drop in place quickly. This was the first supercharger service work I had done, and it turned out great. ~7 years later (and 5 years of occasional racing), still runs nice and quiet with no leaks.
I'm not sure where the original write-up with pictures is nowadays, but a text version is in this thread: