jamas-
there are main seals in both axles, its what seals between the pumpkin and the gearing housing. Not difficult to replace, and just keep an eye on your diff fluid and your fine to drive it (if its the seal on the axle)....
"Do Not Seek Praise. Seek Criticism."
"If You Can't Solve A Problem, It's Because You're Playing By The Rules."
"The Perosn Who Doesn't Make Mistakes Is Unlikely To Make Anything."
-Paul Arden
if its the rear main seal (the front axle has multiple seals, and they call that one the rear main), then its only about 10 bolts i thinkthen they put the new seal in, and bolt it back into place.
any axle should should be able to take care of it for ya. just check your fluid before you drive it and make sure you havent lost too much.