You might want to get the gasket at the axle flange if he's separating the drum from the axle (likely). Only 1 per side is needed, the one between the axle flange and deflector won't be needed as it's held on to the axle flange by the pressed in wheel studs. He will need to open the differential cover to get the axles pulled if you're replacing wheel bearings and seals. The spider shaft and block need to be removed and the axles pushed in to remove the "C" clip, then the axles can be pulled. Get a new gasket for the diff cover.
If he doesn't know that he needs to open the diff, then maybe you need another mechanic.
