The rear differential is really simple. Unfortunatly, you have to take off the rears cover (no drain plug), and let it it drain like that. I would recommend taking out all bolts except one from the top (except having it screwed in just a little, not all the way) and then taking a screwdriver to pry the cover off and allowing it to pour into whatever your using to gather up the fluid. Then once the heavy flow of fluid has stopped, unscrew the top screw and take the cover over to a bench or just to the floor and clean it (the inside that is). You will also want to take a razor blade and clean off the gasket/silicone off around the edge of the cover. If you can't get it off too well with the blade, use a wire brush or a wizz-wheel. Also clean up the housing/casing of the rear end of gasket/silicone crap. I would buy some brake clean for cleaning out the differential. You should spray down the Ring and Pinion including the bearings and then try and whipe out as much goop as possible at the bottom of the casing. Once it has stopped kind of dripping over the edge...use SILICONE (I recommend silicone over a gasket anyday for this type deal) and run a continious bead along the cover. Then spread it kind of evenly over the whole edge and let it sit for about 5-10 mins. Then make sure the surface is clean on the housing, and get 2 bolts and try and line up the cover as best as possible first - try not to smear the silicone all over the place. Then put a bolt in the right and left of the cover and screw them in a bit so you can get your rachet to tighten the bolts up. They do not need to be but so tight, but snug. I would say around 20-30 ft lbs. After the cover is tight, there will be a plug to the right of the driveshaft on the front of the differential. It takes a 3/8s drive rachet, and you should be able to break it loose with that. You will more than likely need 5.5 pints of gear lube. Fill it up til it starts to come out of the fill plug port and then put the plug back on and this one you just want to snug. Do NOT overtighten or you will not get it back off! Check around your cover and make sure nothing is leaking and you'll be good to go for 70-100K. Also, do not be light on the silicone, use it, but don't go too heavy on it!
Good Luck! It's quiet easy!
-Drew