FYI: That supplier no longer ships to the USA.Oh sorry, there's one thread that I made mental notes from:
MBWorld W221 Android discussion
Lots of interesting stuff to read in there, much of it doesn't apply now that these units are plug and play. Wound up purchasing this unit;
632.77US $ 22% OFF|Qualcomm 10.25" Android 10 Car Radio Bluetooth Gps Navigation Head Unit Display For Benz W221 2006-2013 S65 Sg5 Amg S280 S550 - Car Monitors - AliExpressSmarter Shopping, Better Living! Aliexpress.comwww.aliexpress.com
There are MANY to choose from but these guys had a good feedback profile and others on the MBWorld forum had used them. I had one issue with the video converter which just stopped working after a month. They sent me a new one and all is perfect now.