How to rebuild supercharger on 99 pontiac grandprix gtp?

rebuilding isnt hard. make sure you have the time and experience though. all in all its a simple process. most likely your ball bearings are worn or the coupler setup has loosened due to high miles (notice rattle noise in s/c cone and vibrations) -- depends on miles -- m90 eaton s/c which your car has is guranteed to 100,000k miles after that work could be beneficial. any qualified mechanic who knows a thing or two about a s/c can tell you whats wrong. but its one of two problems i mentioed. 1- ball bearings (there is two in the snout) or 2- coupler setup which holds the bearings in place. those parts will need replaced and at that point you might as well replace both anyway for efficiency. you will also need gm s/c oil to reoil your s/c a specialist could help you with the actual surgery.