I need to change the valve cover gasket set on my 1982 280e because oil is leaking out through the center triangular gaskets into the spark plugs and causing some of them to foul (I think). While I am at it I think I ought to adjust the valves. I doubt that it has ever been done on this vehicle which now shows 132k miles. How difficult a project is this? Will I need special tools? Would I be better off taking it to the dealer/independent, and if so, how much should it cost? Any advice would be much appreciated.