How do you replace spark plugs on a 2002 Cadillac DTS?

To replace the spark plugs on a 2002 Cadillac DTS, first, ensure the engine is cool and disconnect the negative battery terminal. Remove the engine cover and detach the ignition coils by unscrewing their mounting bolts and disconnecting the electrical connectors. Unscrew the old spark plugs using a spark plug socket and ratchet, then install the new spark plugs, ensuring they are properly gapped. Reattach the ignition coils, reconnect the battery, and test the engine to ensure everything is functioning correctly.