You need 4 spark plugs. They are located under the cover on the top of the engine. Remove the 4 bolts (13mm) on the cover and carefully unplug the harness on the end of the cover to your right. Pull the cover straight up (you will have some resistance). Before removing the plugs blow out any dirt and debris so that it can not fall into the engine with the plugs removed. Then remove the plugs, I remove and replace one plug at a time. After all 4 plugs have been replaced carefully put the cover back in place making sure the plug wires are in position. Install the 4 bolts and plug in the wire harness.
NOTE: You may want to replace the spark plug wires while you have it unassembled. About $20.00 at a parts store.
Also, do not over tighten the plugs or the bolts on the cover.
About a 20 minute job. if that.