Wheel bearings were more common on the older cars but should be OK by 2002, though with 166k on the clock it could have earned a bad WB by now.
I had a 110k 2.2-powered '98 which was replaced by a 70k 2.5-powered '02. In both cases the automatics seem solid and shift fine, even though they may not be engineering's gift to automatics. The naturally aspirated 2.5 is a much better match to an autobox than it is to the WRX's turbo 2.0. You won't have any driveability worries as a DD. One thing to look for is the AT Temp light being on - that can indicated non-cheap repairs to the transfer case clutch packs are required.
The '02 has a Gen II 2.5 which may still get headgasket issues but they are popularly held to be a small external leak rather than the large internal one in the older 2.5s. The Subaru TSB calls for a can of dealer-issue sealer/conditioner to cure the problem. At 70k mine does not seem to have the problem (yet?).
Overall it is a decent, highly functional little runabout that should last you a while. Mine is a TS wagon I bought for my daughter as a daily but I drive it sometimes just for a switch.
These things hold their value but $2500 seems a little rich for a car on the high side of 150k. Lower mileage will cost more but maybe you can jack him down a little.
