I am getting ready to replace the valve cover gaskets (leaking) on my 2003 Mercedes E320 with 160k miles on it. Since I don't know the service history of the vehicle, I was going to replace the spark plugs at the same time since I'll already be working in the area. Should I also replace the spark plug wires? They look to still be original but I do not know for sure. And what about the ignition coils? Should I replace those also? The car is not currently misfiring or anything.