The XC90 rear differential (at least the one in my XC90) has the same internals as the rear diff on the Land Rover LR2. Land Rover has a rear diff rebuild kit available. I removed the rear diff myself and had Land Rover of Portland rebuild it. The rebuild kit includes various bearings, seals, etc. You can see a stock picture of it here: https://s3.amazonaws.com/atlanticbritish-images/600/FDK004-01.jpg
I also had a failing prop shaft and decided to replace it at the same time with a rebuilt prop shaft from Colorado Driveshaft. Additionally, I decided to take the opportunity to replace the AOC filter and oil pump.
I followed the VIDA instructions for removing the rear diff. The instructions worked well. Since I don’t have a great place to work (just a driveway), and no lift available, one thing I did differently was get some M14 threaded rod from Fastenal to put in place of the subframe bolts (I got this idea from another thread). I cut two 15-inch sections of threaded rod, removed one M14 front subframe bolt at a time and screwed in the threaded rod, with some large washers and a nut on the other end. I did this on both M14 front bolts on the rear subframe. For the two rear M12 bolts, I put some long (150 mm?) M12 bolts and washers in their place. Once all of this was ready, I was able to lower the rear subframe while keeping it securely supported and more or less lined up. It was no problem to extract the rear diff once I did this. And it made reassembly easier later on. You can see a picture of this below.
Working with Land Rover of Portland was a good experience. If any of you use them for this, call up their service dept. and talk with Kim — she was super helpful. They have done some of these rebuilds on Volvo differentials before and knew what they were talking about, and what they were doing. I had to make an appointment about 10 days out, but once I brought the rear diff to them they were able to rebuild it the same day. I spoke with the mechanic who did the work. He saved the old parts to show me, aside from one bearing race that he accidentally tossed. He said that particular race had a lot of wear and he showed me the matching bearing, which also had a lot of wear. But he felt confident the unit itself was in good shape and worthy of rebuilding.
One more note…I originally purchased 12 aftermarket prop shaft bolts from IPD but rounded off a few of them while trying to torque them to spec. I bought factory bolts instead (they take an 8mm hex wrench) and they seem to be much better quality metal than the IPD bolts (which take a 6mm hex wrench, fyi). I personally would not buy the IPD prop shaft bolts again. They also rusted a lot sitting on my car for a week while I waited for the factory bolts to arrive.
Here is a rough idea of what I paid:
Rear differential rebuild (Land Rover of Portland): $550
Rebuilt prop shaft (Colorado Driveshaft): $425
Front M14 bolts on rear subframe (x2 Volvo(?), from IPD): $15
Prop shaft bolts (x12 aftermarket, from IPD): $23 [discarded]
OEM prop shaft bolts (x12 Volvo, from FCP Euro): $29
Front muffler gasket (Volvo, from Tasca): $3
AOC oil pump (Volvo, from Tasca): $269
AOC oil filter kit (Volvo, from Tasca): $22
AOC front pinion oil seal (Volvo, from Tasca): $16
Rear diff oil (Volvo, from IPD): $31
AOC oil (Volvo, from IPD): $33
4-wheel alignment: $79
~$50 for threaded rod, bolts, parts shipping, other misc items
Total above is $1545. So, for roughly $1550 (and a *lot* of hours of my own labor), I have a rebuilt rear diff, a rebuilt prop shaft, and a refreshed AOC/Haldex unit. And new fluids 
I am pleased with the cost, and the result. But I’m not sure I would do it again, because it was a lot of work and a lot of downtime for my primary vehicle.
Here are a few pictures:
