i'll assume you have already read a good repair manual and have questions. if not, please get a good manual and we'll answer any questions from there.
basically, for pinion seal removal: mark and remove drive shaft, measure pinion preload, mark and remove pinion flange nut, use puller to remove pinion flange, remove seal, remove oil slinger and bearing, replace colapsible spacer.
this is a brief howto, a good repair manual will be more specific, have torque specs, etc. and may contain photos.