well i changed the back three plugs and on two of them there is oil on the threads, and the pocelain part. is this a sign of head gasket leakage, or what? an input is appreciated.
most likely a leaky valve cover gasket....
replace the valve cover gaskets and dont overtorque the cover... a common problem. they should be torqued to 8-10 IN-lbs (not FT-lbs...) IIRC.
the head gasket is under the plugs so the oil would have to travel up....