I looked into this for my W210 which is not pre-wired for the phone, the advise form MBenzNL was to fit the newer UHI phone kit and with all genuine parts and new mirror with mic would be 1200-1300 Euro. I decided to fit the Evo cradle to my Nokia CARK-91 kit so it will take all the Pop Port phones and uses the cars audio system but with a seperate mic next to the mirror. Works ok but not fully intergrated with comand.
Check with MB if your VIN had the pre-wire you maybe lucky.