i've noticed that all around the tin flange at the back of the transfer case where the tailshaft starts is wet with oil and that there has been puddles of oil on the ground under it but it only leaked for a little bit then stopped. does this meen its run out of oil? or the seal sealed itself again? what cases the seals to leak? and how hard is it to replace the seal? can it be done at home or does the t/f case need to be pulled out. i also have to replace the centre bearing which is shagged so i will be doing them at the same time.