How do you change the spark plugs on a 2005 Cadillac CTS 3.6?

To change the spark plugs on a 2005 Cadillac CTS 3.6, first, ensure the engine is cool and disconnect the battery. Remove the engine cover to access the spark plugs, then carefully disconnect the ignition coil connectors and remove the coils. Use a spark plug socket to unscrew the old spark plugs, then install the new ones, tightening them to the manufacturer's specifications. Reassemble by reinstalling the coils and connectors, followed by the engine cover, and reconnect the battery.