I had my rear diff rebuilt and it cost about half the price of a new one. Most of the parts had no history of ever being ordered in North America, as far as Subaru could tell. The pinion bearings have no third party supplier, either. So, those will be coming from Japan. Good luck with that. Bad timing.
You'll want to do both pinion bearings, both carrier bearings and retainers. My retainers had to be chiseled off and the new ones sealed with silicone because of the rough mating surfaces. Of course, I didn't find out about the silicone requirement until it was back in the car and made a mess of my driveway.
I'll see if I can find the actual part numbers used.