you have to pull the axle shafts [inner and outer], which means brakes and brg have to come off.
which also means now is the time to do ujoints and ball joints if you havent recently done them.
pull the selector off. once you work the slider out you can pull the inner axle out.
drive the seal out and clean out the housing.
installing the new seal is the hard part. i made a spreader tool with some 1/2" all thread,
a race driver kit and some nuts and large washers. you dont have much room to work in so you cant tap the seal in with a hammer.
i have some old brg races that i use to fit the seal body and not booger the rubber lips of the seal.