oil in spark plugs

I just got a 98 Jetta GLX V6. I had plugs changed and mechanic said it has oil in back 3 plugs. It has 97,000 miles on it. Does anyone have any ideas as to what's wrong. Check engine light is also on now. Valve cover gasket? Head Gasket? oil is clean.

blown valve seals, blow piston rings, somehow oil is getting into the cylider. that would be my two guesses. sorry kid, but 97K miles on a car that was probably ran hard or didn't have regular oil changes, or was run hot, it can happen.

valve cover gasket kit will fix ur problem

oil fouled plugs sounds like u have a pretty serious problem, i'd suspect head gasket, or valve stem seals, usually stem seals get hardened after time and allow too much clearance for oil to lubricate the guide, but it has to be pretty severe to foul the plugs, check the head gasket