I have a little wiggle in the top (t-case end) U-joint on my rear d-shaft.
Any tips/info on replacing it? Better off just dropping off at a driveshaft shop?
I looked through the FSM, procedure dosn't look complicated... but refers to an odd SST for getting the cross/spider gear out.

my personal experience:

drop it off at a driveshaft shop! mine were next to impossible to get out. they are extremely beefy.

dont forget to mark the shaft position on the flanges so you dont have out of phase issues when you put it back on.

On one hand, like snowman said, it can be VERY difficult to remove. It makes life much easier to let a shop do it, and it should only cost you $20-$30 bucks or so.

On the other hand, sometimes they come out fairly easy, and you should really know how to do the job in case you pop a ujoint on the trail or something and you need to do the repair yourself.

I say attemp it yourself, if you cant get it right yourself, stop, and take the shaft and ujoint into a shop.

As for the phasing issues, just dont separate the shaft at the slip and you wont have a problem. The position on the flange at the tcase or diff doesnt matter.

Dosn't it have one wide spline or something so that you can only slip it back it at the right orientation? I seem to recall running into that before.

Usually not, all the ones I have seen are the same splines all the way around. Usually best to paint a mark across the slip yoke to help you re-align it in case it comes apart, or you can re-phase the u-joints if needed:
http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml#Phasing

another recommendation for driveline shop.
I did them once on a 2wd truck without issue, but when I tried to do them myself the first time on the 4wd, I ended up bending one of the yokes.