I usually go to ebay and type mercedes radio or mercedes s. Those tools are pretty popular on there now. As far as going to the dealers,they all seem pretty unfriendly when it comes to do it yourselfers and answering any do it yourself type of questions. I tried to purchase one from Mercedes of Westmont In ILL. And they told me they didn't have one. So Ebay has been a good resource for me ....No Attitudes