Fitted one of these to my SLK today. Order the correct harness and the rest is straight forward. Remember to get the aerial convertor too.
What Merc are you trying to fit it into?
Also Check on Ebay for the fitting kit which will include the fascia to match into the dash.
Check on YouTube to see how to get the dash apart.
Thanks for reply. I really want to get it set up, it looks great in the slot. I bought a harness, fascia and patch lead. I need the stalk control adaptor. I have removed old stereo so I know how to take dash apart. Did you have to take a 12v supply to it? Mine is a 04 c200 sport coupe.