I've done the diffs and t-case on my FJC twice. Not a big deal but I did make a bit of a mess draining the front one. I used Mobile One 75w90 in all three. You'll need to get the bottle pump thingamajig as you won't have room to tilt the bottles up to pour the fluid in. I've never changed the AT fluid on my own as it seems more of pita than it's worth.
Jesse over at ATLR is super reasonable and a great guy to work with if you want to have someone else do it.