Q&A

 Master

There are two stereos listed. Have you checked the fuses? Mercedes wiring diagrams are a little complicated to rad (but not too difficult). There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online
Alldata show the fuses that supply power to the radio, it shows stereo removal, and how to test for voltage at the specific pins at the back of the radio. Go to A/Z search type in stereo, then select "electrical diagrams" and later look at "connector view".A lot of places specialize in the repair of original factory equipment stereos, you will find them online and be able to get a quote.

 Master

Check fuses, if these are ok your problem is probably a blown out amplifier which will need replaced. Check outputs for power on amp.