Valve Covers

Hi I just ordered valve cover gaskets and the grommets for my moms 1998 Z28 Chevy Camaro. It was 24.00 dollars everyone else wanted 30 plus dollars for it. My question is how long does it take to change out both valve cover gaskets and the grommets. This is my first time ever of doing a valve cover. Also these gaskets have never been changed ever since we bought it. I saw the valve cover leaking on the right side the left doesnt leak. The right side is wet down towards the side of the cover. It is also hitting the exhaust and you can smell the oil burning. Thanks.