the mileage isn't low by any means....but that's a pretty decent price for an xle that seems to be in excellent opinion.
the only thing to really look for- you already saw. these engines have a habit of leaking from the valve covers, but nothing astronomical or damaging. They just need a change every 100K or so (if not a bit less).
At this point, just out of principle, I'd try to deal him down a bit just because it's about time for a timing belt/water pump, seals, pullies, change, etc. so general maintenance that he can't guarantee has been done.
If he can go down to $3K, I'd pick up that gem