Unfortunalty, oil leaks can be difficult to issolate. Commonly they come from the valve cover on this vehicle, but the best step to take is to have the engine degreases, then flourecent "leak dye" added to the oil. When it leaks out it will leave a "glow in the dark" trail of the leak when viewed with an ultaviolet lamp. Most quality shops and dealers have the ability to do this procedure. Thanks,
If it is a leaki from the valve cover, than a valve cover gasket is replaced, which is considered a minor repair compared to the other major items which can leak oil.
Often a engine is so covered in oil and grime from the road, a leak could be originalting from underneath the grime/grease, and is difficult to locate. Therefore the correct measure to take is degrease (or steam and pressure wash the engine). Than the oil can be changed and fluourecent dye added.