ML350 as in Mercedes? The first place to start is the Mercedes manual or give the dealer a call. My wife's fun car (as in too many kids, the minivan sucks I need something cool to drive car) is a 1998 SL500 which is a great car but wow is owning a German car an education.
You'd better hope you don't need a bracket, a harness or anything else from Mercedes to pull off the intended operation or you'd better plan on re-financing the DP. Because parts at the Benz dealer pretty much start in the thousands and go up from there.
In all seriousness check out the manual. I know mine is very specific about just how it can and can't be towed.