Yes, there is a part from Mercedes to be installed in the cdc space that is left empty. You can order it from your dealer. Is a very cheap part. Now, regarding the opening of the compartment there is no solution from the Mercedes. Threre is a solution aftermarket. There is a very reliable company in Germany selling those interfaces. I order mine when I did my conversion from AUDIO 20 to NTG 2.5. The intreface module was integrated withing the wiring conversion. The company is
Kabel Daviko. Explain the problem and they will tell you what do you need.