2004 Caddy CTS used the same engine as the Caddy Catera of 96-2001
And yes, you do need to take off the manifold to get to the plugs
Wait till you have to do the timing belt, which should be done very 60K or less
We had a Suzuki Samurai many years ago. Easiest car to service, ever.
Timing belt took me 30 minutes to change.