those are a pain to change. check your balljoints for wear first. if the balljoints are worn you can replace them when you do the axle seal. the internal axle stubshaft is held in with a snapring. if the balljoints are good the easiest way to access the seal is to ubbolt the axles, driveshaft, steering linkage and all the diff mounting bolts except for the rear one. this allowes you to swing the diff down and pop out the stubshaft and replace the seal. you might want to get a shop to do this as it's a hell of a lot of work and will take a long time if your not used to this type of work. if i remember right a shop will charge about 2.0 hrs.
hope this helps