Az1aN

What changes were made for a '10 ML63? Debating if I should be hard headed and stick with shopping for a '10 model or downgrade to a '09...

serendipity

Very little. Between 08 and 09 the model was facelifted and COMAND was updated, among other tweaks. After that it stayed virtually unchanged until this year's redesign.

ULJets

I'm not aware of any changes between 2009 and 2010. 2011's have new blackout headlights and a new hood. And of course 2012 is a whole new design.

Az1aN

What year did they start doing 2 tone (black/white) color interiors?

ULJets

The 2-tone interiors were only available on the 10th anniversary edition in 2009 and the performance edition. 2012's can be ordered in the Designo Porcelain which is a 2-tone black/white interior as well.
I searched for over 6 months trying to find a anniversary edition ML63...finally settled on a regular one as they are impossible to come by.