how do you rotate a 2000 ML 320 crankshaft pulley
 

I want to change the transmission oil myslef for my 2000 ML 320. I followed the DIY article at http://www.peachparts.com/Wikka/Trans7226Fluid but stuck at the step to roate the crankshaft pulley to drain the torque converter because I could not find a nut in the middle of the crankshaft pulley to rotate. I must have missed something because the pulley has to be bolted to the engine somehow. I also looked up the DYI site at http://www.whnet.com/4x4/shoptalk.html but still no hint there. Any suggestion?

i believe 2000 and newer do not have the torque converter drain, you can usually turn it with a 27mm socket clockwise to verify

I got a 27mm 12 point socket and it would not lock into anything in the middle of the pulley. I took a mirror and look into and saw a round nut with a big hex hole. Do I need a very big hex wrench to turn it?

then it has been changed to the new style, which is a 17mm allen