Did you smell the plug you pulled to see if there was any coolant smell? Blown headgaskets aren't a common problem with these cars, but it's a thought.
You more than likely have some bad o-ring gaskets, causing a lot of oil to seap onto your plugs and foul them out. You'll have to pull the intake manifold and the valve covers to replace them. This is a good time to replace the valve cover gaskets themselves, as well, and to clean the upper and lower intake manifolds, too. Depending on the age of the plugs, they're probably in need of replacement as well.