I did not have any problem with shims.
I think that output gear/shaft assembly (shaft above the center diff), has a couple of shims, but they are pretty big, so you shouldn't worry about loosing them too much.

If you assemble it in the same way you disassembled it, there should not be any problems.

I had more problems with shifting linkage, prop shaft and exhaust removal than with disasembly and asembly of the diff housing and replacement of the diff itself.

So will you just replace the diff with the same model or will you replace it with the older model diff?

Also, before you begin, read the Workshop/Service manual. I'm writing this purely out of my head, so I almost certainly forgot something....