This is about the same mileage I had when my O2 sensors started going. The upstreams seem to die sooner/more often than the downstream sensors. The parts are like $60 each at autozone or oreileys but probably $80-100 at the dealer. Bank 2 (front) can be changed in 15 Min. Bank 1 is harder to reach but a decent shop should be able to do it in an hour tops. Those CELs won't hurt your car but will probably drop your gas mileage a bit.
