Welcome,

First, how many miles? There are many here that have way more knowledge than a dealership. The always cause more damage than good. It does not sound like the screem. The first thing I would do is send the RCM to DJ Tighe for a complete rebuild. It is only about $50.00 plus shipping. Do a search at the top of this page for RCM and you will find his contact info. If it does turn out to be the screem, send it to SOS Diagnostics and have it repaired. They have info on their site. Be thankful you got it out of the dealer. If you ever need work done, use an independent Mercedes or european repair shop. There cars are Mercedes SLK 320s mechanicly.