One spark plug is not working, causing the engine to miss while driving. I don't know if all the spark plugs need to be changed or just the one (number six spark plug is not working). Also, the valve cover gaskets leak and the oil pan leaks.
A cylinder #6 misfire doesn’t necessarily mean the plug is bad. There are many other things that could cause a single cylinder misfire, from a faulty fuel injector to an engine mechanical problem. Anything that causes incomplete or abnormal combustion could be the cause. If your valve covers are leaking, there is a chance that the spark plug tube seals are allowing oil to get into the spark plug hole. This could cause a misfire and contaminate the plug. If the #6 spark plug is indeed causing the misfire, I suggest replacing all the plugs since the others are probably worn as well. I recommend having a professional, such as one from YourMechanic, inspect your vehicle firsthand. They will be able to determine the correct repairs and replace your spark plugs if needed.