This weekend I replaced the fuel filters and injector hoses. I didn't prime the secondary filter so I killed the battery trying to get it started. My radio now asks for a "CODE". I contacted the previous owner and they stated that it isn't the original radio that was installed in the vehicle. It is in fact a Mercedes factory radio. 1)
Where do I find the serial number or ID? 2) If I need to remove it; how is that done?

 

Actually when I removed the radio from the console, the code was written on it. Problem solved.