I'm going to guess its at least a post 2005 truck, not a diesel.

the regular stalk on that side is for the wipers and their control

drivers side is turn signals and cruise control

I'm searching the internet for what ever I can find on ML320 control stalk and I keep getting complaints about cruise and turn signals location and hits about how you can shift gears with the buttons behind the wheel and a short stalk on the right side of the wheel .