probably leaking out of the pinion seal, but if it is diff gasket, disc onnect brake lines remove 4 bolts on each backing plate slide axles off remove diff nuts, clean reasemble. 45 minutes
It's not that hard but it's a pita. I'll just add to what cperry said above.
1) jack up axle, put it on jackstands
2) Remove tires
3) Remove brake lines
4) Remove 4 bolts that hold axle in place
5) Pull out axle (do not let them sit hanging halfway out, that ruins the oil seals)
6) Remove 4 driveshaft bolts
7) Remove 10-12 bolts on third member
8) clean surfaces, install new gasket, reassemble
I like to use gasket maker and a gasket. If you replace it again the surface will be easier to clean up and I think it seals better. Also, use lock tite on the third member bolts. I'm not sure if you have to wait for the gasket maker to set up. I'd just follow the instructions on the tube.
Pay attention to the studs hold the chunk in place, besure they are all threaded into the axle housing properly, if a stud comes out with the nut, reinstall stud BEFORE you reinstall the chunk.
Pull the threads on the housing and you'll never get it to stop leaking with out some not so fun repair work.
Also, don't over tighten the nuts, or you can also pull the threads on the housing.