ouch. that sucks because that is a nasty job.
on the 1992 big bear i did that seal on, i had to remove the rear diff, rear swing arm (check the bearings while it is out), rear drive shaft, front drive shaft, and then you can unbolt the transfer case. take care to mark where the shims go for the transfercase as they can be different thicknesses and have to be placed back exactly where they came from and there is no easy way to mark them as space is limited. you also (if memory serves) have to unbolt the tranny output drive to finish removal of the t-case. there are 4 or 5 bolts to remove the cover whitch is above the front drive shaft by where your left boot rests. once it is out, you have to split the case and remove the bearing and seal together. i can see the whole job taking 8-10 hrs with all the parts in hand. i did not have all the parts i needed.
install is the reverse of the above. i recoment avaition form-a gasket for the trany drive housing a there is no gasket availible. would have made our lives a lot easyer if they had held the seal in with a heavy snap ring instead of driving it in from the rear with a really heavy duty lip on the case protecting it.
i would scan the pages for you out of my clymers manual but my scanner is giving me issues atm.