Engine is misfiring?

Hello,

If you have oil in the spark plugs it will cause the plug to foul out and it will misfire.
So you will have to get the oil leak fixed in order to take care of the misfire.
Its likely that the valve cover gasket is leaking and that's why you have oil in the plug.
To replace the gasket you will have to remove the valve cover.

https://www.2carpros.com/articles/replace-valve-cover-gasket

I have attached diagrams for your reference.

Please let me know of any questions.
Thank you.