A 92+ XJ should have it (YJ had disco all the way), and a TJ but I think it's been said not ALL 92 XJ's had the one piece. You can leave your original housing and fork in place, it won't contact the one piece shaft, it's much much smaller there, just take out the shift motor and tape up your wires so they aren't hanging around, and make sure you plug off the vac lines. It's a fairly easy swap, only hard part I think you'll have is the c-clip on your axle shafts, and the hub hehe, which isn't too terrible, maybe you'll get lucky tho and it's not c-clipped, I was expecting mine to be but it wasn't.
As for the process:
1: Get a jack and jack up and put it on stands
2: take the diff cover off and drain fluid, pop out c-clip if needed
3: take the wheel off
4: rotor and caliper (13 mil)
5: hub. This one's tricky, the cotter key can be a bugger if it's old, and then the spindle nut is rather large and might need some oomph to get it off.
6: get your shift collar housing off, motor, etc and start feeding the outer shaft out, remove collar, push the inner out.
Installation is simple enough.
Couple things to mention, make sure you install seals, part number for the pass. side is 471763. That's a Federal Mogul National p/n, should be able to cross that at any local part store. The caliper bolts are incredibly easy to break fyi. Good luck!
Also, here's a write up for a YJ, it's the same process.
http://www.stu-offroad.com/axle/yjd30convert/yjconvert-1.htm