[C230 Sport Coup]

No clamps?
Hmmm....
On the C230 I believe there's 5 hoses.
The DVD manual recommends using clamps on the hoses.

For me, I didn't completely pull the old filter,
IMHO it's better to do one or 2 at a time so you don't get confused as to placement, and you can clamp them off to avoid spillage.
You can buy special little hose clamps at most auto parts stores that
sell tools, but I used vise grips (not too tight) and some other clamps I found in the bargain tool bin.

Before starting the car, I turned the key to the 2nd position,
let the fuel pump kick in, and waited for a minutes to let it pressurize.
Not sure if this helps or not, but I didn't get an CEL's and others have.