Hello, I was going to check and change the spark plugs on my car due to some rough idle problems that previous posts have also mentioned. The car has approx. 110k MB serviced and was wondering when they are usually changed or at what mileage are they changed according to regular service (should wires etc. also be changed)? What is the exact oem spark plugs I should purchase and what is the gap spec.? This is a very novice question but do they not come at the correct gap spec and how should one go about adjusting them? Finally could someone tell me what I should torque them to?