[cstreit]

Yes, you can get to the gasket without removing the housing. Beneath the sprocket and the flange (that the pin locks into) is an aluminum plate with a U shaped cut in the edge for the o-ring. Behind that is the gasket....

I would put a light coat of curil-T on both sides of the gasket to ensure proper sealing since there's very little torque on that aluminum plate and it's such a pain to get to.