The location of the oil drain plug is on the bottom of the oil pan, towards the front of the engine. You'll need to get underneath the car to access it.
The oil filter for the 2005 Cadillac STS V6 (3.6L) is located on the passenger side of the engine, near the front. It's typically easily accessible from the top without removing anything else. However, the exact location and accessibility might vary slightly depending on the specific options and modifications of your vehicle. Consult your owner's manual or a repair manual with diagrams for a more precise location.
