Howdy. I have a 1998 3.8L G.P. Bought her new, just hit 197,000 miles. Aside from the normal wear and tear items she is solid. Never leaked oil until now. Appears to be coming from the valve covers. Here's my question(s). How many miles can I expect to get until the valve cover gaskets go bad? Can someone give me the step by step and any pointers in doing the job myself? (I've got tools THANKS!