2008 Aveo oil in the plug gallery?

I just started having an issue when winding up through the gears I'd get a hesitation? It didn't throw a code or check engine lighht but Chevrolet garage said plugs should be changed at 30,000 miles and mine has 66,000 so I set about changing them. First I had to buy a special socket extension combo to fit iside the spark plug bore. All plugs came out okay but I noticed a large amount of engine oil in three out of four cavaties. There was engine oil on top of the valve cover . I just had the timing belt and water pump replaced by Chevrolet dealer weeks ago and air conditioning installed last fall. Could this of happened when changing those parts or is it a simple leaking valve cover gasket that needs changed?

Also can anyone give me a heads up on how hard is it to change thew fuel filter. My car is an 08' Aveo Special edition 5.

Thanks Wardie

Valve cover gasket. Common problem on the E-tecs, and a cheap fix

I just found out that the only fuel filter for a 2010 is connected to the fuel pump in the tank. It is normally only changed out when there is an issue. If you are having an issue with low fuel pressure, I suggest cleaning your battery terminals. I was having an issue with my throttle being mushy and smelling raw fuel. There was no external leakage. I never checked to see if the fuel pressure was low, but I believe that it was and therefore was not spraying out the the injectors correctly. I noticed that the positive battery terminal was getting hot. I cleaned the terminals and replaced the positive terminal with a heavy duty version similar to the one at this link: Amazon.com: METRA Ltd GBT2N Gold Series Battery Terminal: Automotive
I wire brushed the metal brackets, including the one with the 100 amp fuse on it. That seemed to correct the issue.
Good luck!