My car has been sitting for about a month. I moved it Wednesday to get another car out and noticed a pretty distinct smell. I did not have time to investigate, and thought nothing of it. My mother drove the car on some errands and the smell came back. She took it to an oil change place and they said the valve cover gasket looked bad. I looked at it when I got back into town and the front of the driver side head is covered in burned oil and there is some splatter on the engine cover.

Is this common? The car has sat for a month, and I did not notice the smell when it was parked.