I agree with RPM. Replace the filter & gaskets. Its easy to do. While you have the filter cap off, look closely at the plastic threads and make sure they haven't been damaged. That cap is only supposed to be torqued to 25nm, which translates into 18.5 ft-lbs. That's not much more than hand tight. If you see any damage at all, spend the $60 or so and buy another one.

My guess is that the last mechanic forgot the top o-ring and just cranked the cap down nice and tight.

Edit: Use the appropriate sections of this link to get the cap off and re-torqued.