How do you replace spark plugs on a 1993 Cadillac Deville 4.9?

To replace the spark plugs on a 1993 Cadillac Deville 4.9, first, ensure the engine is cool and disconnect the negative battery cable. Remove the ignition coil and then the spark plug wires, labeling them for reinstallation. Use a spark plug socket and ratchet to unscrew the old plugs, then install the new plugs, ensuring they are properly gapped. Reattach the spark plug wires and ignition coil, and reconnect the battery cable.