Hi and thanks for using 2CarPros.
Most likely, the misfire was caused by the oil leak. It isn't normal to have oil there, but it isn't uncommon. The valve cover on this vehicle has o-rings where each spark plug goes down into the head. The o-rings can start to leak and cause oil to gather in the spark plug well. In the event this is happening, a repair would require removal of the valve cover and replacement of the gaskets and o-rings.
The directions for removal and replacement are in pics one and two.
Let me know if this helps or if you have other questions.
Images (Click to enlarge)
Saturday, February 23rd, 2019 AT 5:46 PM