Can the valve cover gasket on the 1999 sportage be replaced without taking the plugs out. In other words, what's the least amount of work that has to be done to replace the gasket. The plugs were changed a little bit ago so the least amount of work the better. It's starting to leak pretty bad at 70000mi. Also, I see that the new gasket isn't flat. Does it fit into a channel and should I use a little silacone? Thanks all.