Replacing the rear pinion seal is no biggie at all, in fact O'Reilly Auto actually carries them in stock for like 12$ and takes about 20-25min. to do depending on how skeptical you are of cleaning it before putting back in. Just removing the 4 8mm bolts holding the rear u-joint to the pinion flange, use a 1/2" dr. impact and a socket to take the nut off, and pull the pinion flange off, mine slid off, but you can use any harmonic balancer puller to remove it. Old seal can be pulled with a flathead screwdriver or a seal puller bought for about $10 at about any parts store. If when you pull the flange and see a groove in it where the seal is riding, you can take it to the parts store and most good ones like O'Reilly will mic. it and be able to give you a sleeve to cover up those grooves to keep it from leaking again.