It's common on most cars to get some oil accumulation around the PCV lines, so removing them and flushing them out with mineral spirits periodically is a good idea along with cleaning up any oil film inside the air cleaner housing.
Not sure if your system is configured the same, but my '88 190E 2.6 has a circulation system that draws fresh air through air cleaner, circulates it through the crankcase where it picks up blowby and then into the inlet manifold through a restrictor.
During less than WOT operation, manifold vacuum keeps the air circulating "forward", but flow at high vacuum is limited by the restrictor. During WOT operation since there is little manifold vacuum, the flow can actually reverse, which is why a film of oil will buildup inside the air clearen housing.
Since a rocker arm is right under the oil fill cap, if you remove it while the engine is running it will fling oil. The "vacuum" in the crankcase due to the PCV system is, at most, an inch or two H2O, and upon loosening the oil fill cap, the very small crankcase vacuum immediately bleeds down to zero.
Don't know about the electrical component you refer to, but I doubt if it's part of the PCV system. The are several sensors and switches mounted along the inlet side of the head, next to the cam cover.