I did mine on the XJ.. wasn't too tough...
I'd recommend going to the dealer and getting a new o-ring for the oil pump pickup tube... having a new, stiff o-ring will help hold everything together...
It really helps if you have another set of hands helping get the case back together... you can do it yourself, but getting everythign lined up, making sure the oil pickup tube is seated in the oil pump and getting the splines lined up was a bear...
It is TOUGH getting the oil pump on the heavy duty splines... it looks like the splines are too big... but they ain't...
Take your time.. you'll be fine.
Oh yeah... one little thing that will help...
The instructions tell you about the weird 12 pt 10mm bolt on the top... well, there's a nut on the front side of the case holding on a bracket... take that nut off first... trying to back out the bolt without knowing about the nut on there about broke my forearm...