The 1st thing you need to do with a GT is remove the filter in the oil feed line to the turbo. It gets clogged and kills the turbo. Subaru issued a service/tech bulletin #02-106-08R that you can Google. Subaru recommends replacing the filter but you don't need it so just remove it. Its in a banjo bolt. You can but the same banjo bolt without the filter for about $5 and you're done. With only 49K miles the filter is probably getting very dirty.
The diffs need to be serviced regularly so just make sure that its been done. Sound like a nice car. Good luck.