Yes, you have to take the cover off. I went to the dealer and they sold me a tube of adhesive to use to reseal the cover, it was around $9 bucks & the part # is 12346141. I'm sure you can use other stuff I just happen to be there for something else. Hope this helps.
There is no drain plug! To drain the diff you have to take off the cover and have a big pan under it to catch all the fluid. aftermarket company's do make diff covers with drain plugs though. There is a fill hole on the front of the diff more toward the top were you fill it after. [img]images/graemlins/chair.gif[/img]
I just put on an aftermarket diff cover on my 9.5" 14 bolt. To seal it back up the recomended stuff is RTV sealant. Its like 6 bucks at Kragen (a horrible place w/ crappy service [img]images/graemlins/chair.gif[/img] )