Hi Adam,
I have a 2006 ML. The product you are looking for can be found at NAV TV. There web address is
www.nav.tv .
They provided me with the right product for my ML which enabled me to install a digital TV tuner. The product uses fibre obtics to incorporate with a MOST system. It also activates the video button for selecting the aftermarket product so no switches.
Im sure they can help you with a solution.