The plugs on the M103 engine are very easy to replace. The key is using the proper spark plug wire puller (I own the Hazet tool which grabs the plug wire down on the metal part). Rotate the plug wire a little bit while it is still on the plug before gently and firmly pulling off the individual plug wire. Clean out the inside of the plug connector (I used cotton swabs with a little alcohol). Then, use a good quality spark plug socket, make sure the socket is completely on the plug, and slowly but firmly loosen the plug turning counterclockwise (I used a 1/2 inch ratchet with a 1/2 to 3/8 adapter to get a little bit better torque). Remove the plug and check its condition. Check the gap on the new spark plug (.32-.35 inches), then put a small amount of anti-sieze compound on the spark plug threads. Put the plug on the socket and carefully, by hand, thread the spark plug back into the hole. It should thread easily. Next, using a torque wrench, torque the plug to 15 ft/lbs. DO NOT OVERTORQUE!! (I did all this with a cold engine). Before you put on the plug wire, take a cotton swab and put a small amount of dielectric grease on the tip of the newly installed plug. Take the plug wire and firmly push it onto the spark plug. You should hear or feel a click to let you know that the plug wire is completely seated on the spark plug. Hope all this info helps.