Gasket

It's the valve cover gasket, spark plug tube seals and valve cover hold down bolt seals that should be replaced. The parts are about $45 to $60, labor to replace is about .9 to 1 hour. While there you should adjust the valve clearences as you have the cover off anyway.

To replace the Valve Cover gasket and spark plug tube seals is one hour labor and the cost of the gasket set.