I did a search for changing the fluids in both of these and really didnt come up with a good answer. Also doing my search made me realize I havent been maintaining my veh. very well. The only thing I changed was my coolant @ 40000 mi. So...

Do the fluids in the Differentials need to be changed? If so, what kind of fluids?
and
What kind of fluid to put in the transfer case? And how often should it be changed?
Also
I tried using that stupid tool to change my fuel filter, but couldnt figure it out. Am I just clueless and its just that easy, or is there a trick? When I took it to a friend mechanic, he had it out in about .5 sec.
I was going to do my own tranny fluid but I guess its better to have it flushed. Same w/the coolant.
On the plugs....Ive read the horror stories and I know what to expect. Im away from my truck right now and am wondering does it take a special socket to remove them or will a regular plug socket do?
Sorry for all the questions, thanks for any replies.