Mercedes are notoriously known for the most complcated wiring harness on earth. My friend had a C230 kompressor and wanted to install a cd player in it. No shop would touch it just to install a dash unit or changer in the back. They said take it to dealer and have them install the factory setup. I wouldnt not be surprised if there would be a lot of issues with the engine harness mixing with the body harness and how things are controlled or them even working with the engine missing.