oil on the spark plugs is bad... sorry to be the first to reply...
The combustion part of the cylinder is seperated by the oil and compression rings that surround the piston inside the cylinder. If the rings are bad oil can pass around the rings and get into the cylinder.
The valves guides are another source for oil to get into the cylinder. Valve guides are attached to the heads and are what hold the valves in place, they also serve to keep the oil by the rocker arms in its place.
If the spark plugs are fouled by oil, then you are probably burning oil. This will be seen at the exhaust pipe. Also, did all four spark plugs look the same?? You might want to install a new set and run them for a week and see what the results are (this is a good idea if you just acquired the vehicle).