It's the cover right on top of the engine. It has three torx screws holding it down. There is a coil on top of every spark plug. these are held in place with two screws (bolts) each. Each one of these coils have a gasket that is probably pretty rotten and unusable a second time. I made new ones with gasket material and coated them on both sides with silicone sealer and let dry. I don't know if auto parts stores stock them or not. I'm sure the dealers do.

The coils have a rubber boot that attaches to the spark plug. You should loosen each plug a few turns and blow out the recess with compressed air to get rid of any grit or other material there and then remove the plugs.

 

Those coils are ignition coils. No they don't have to be replaced during a normal tuneup. I have never had one fail, but i believe other owners have.

Instead of one coil supplying spark to all of the plugs, a lot of newer vehicles With computer controlled engines have an ignition coil for every spark plug.

Doug