Ford Expedition Rough Idle, loss of power?

I was tuning up my brother's 1998 4.6L Expedition because the check engine light was on. On cylinder number 7 the plug came out with rust, grime, and the deep area where the spark plug goes into was filled with oil. If you know this car, you know how wierd that is. Does this mean a bad cylinder. The tune up did not fix it it, but I have not done the EGR, PCV, or fuel filter yet. Anybody ever have this type of thing, and what did it mean? Thanks a ton...