You can make a gasket with some gasket paper obtained from an auto parts store. Just get a small ball peen hammer and lay the gasket material against the edge to be sealed on the cover and tap. I've done this many times in the past on engines when gaskets weren't available. Once the outline if made, you can cut with scissors if needed.
You can also repair the plug wire by cutting a half inch off the damaged end and crimp another male end in place. It should contact the core of the plug wire.
