This sounds dumb but how do you remove the top cover on the engine to access the air filters? Also check engine light just came on yesterday my clk is a 1999 just turned 20k miles rarely driven.
top cover on 1999 Mercedes-Benz CLK430
Go to auto zone and buy your filters and they will show you how its done
There 4 big clips kind of in a square pattern and 1 small clip in front of the star. Pull it up gently with slight force, use a flashlight and you can see the clip. As for your CEL get the diagnostic code.