Well, BillK is correct, I'll chime in with the correct way to do it. DZ has been lucky, and it can be done that way, but it is not the correct way by any means!
When customers come into our shop and ask if we will replace the seal, we tell them it will cost $185. That is the labor charge that we charge to disassemble a rear, clean it, & put it back together with new fluid. Some of them are shocked and reply that "so & so shop" down the street said they'd do it for around $50-75, why are you so high? Then we explain to them the importance of the crush sleeve, and doing the job correctly. We offer them the option of taking it down the street for $50-75, or having us do it right. Some of them go down the street and some of them have us do it right. Those that go down the street have ended up back at our shop with bad pinion bearings shortly after, and then have to pay for that repair.
Here is what we do for $185 labor:
Disassemble, inspect all bearings, clean axle tubes out, install new axle seals, new crush sleeve, new pinion seal, reassemble, fill with new fluid. We usually always use the same nut, but we use red loctite on it. We also do not use an inch-pound torque wrench, ever. We tighten the nut with an impact, and use "feel" to get it correct. With used bearings, we do not tighten as much, but with new bearings, we tighten the nut so there is more drag. We also use red loctite on the retaining bolt for the spider gear pin. We never use a gasket, silicone only.
Someone had posted something about the gasket on an 8.5 ten bolt as having slots in it to allow for axle bearing lube. If you use silicone only, the holes in the axle tube will be open, as the cover has little dimples in it to allow lube to deflect into the holes and down the axle tube, so that point does not matter. Anyway, I recommend silicone in place of a gasket. We never have a problem with leaks.
There are shortcut ways, and there are correct ways to do a lot of things, but for a rearend, the parts can add up pretty fast, so I would always recommend using a new crush sleeve any time the pinion nut is removed, or loosened, for any reason.
Sorry, so long, but had to "chime in"
70 & 1/2 RS Camaro
SB406 & M20 4spd
SB350 & TH400