No, 145K isn't high, although I would wonder about the care the auto tranny received, as with any used vehicle. Isuzu fixed a piston oil ring problem sometime in 2001, supposedly the motors with the fix have a screw-in PCV valve, and the older ones have a push-in PCV valve. But there are plenty of Troopers out there that have this "problem" and are still going strong.
There is no problem with common parts. Hard to say about more uncommon parts like engine internals, haven't heard of problems though.