I can confirm for my ML430 a 1/4" E8 Torx is required and NOT an allen wrench.
You might want to take a look at the Bosch website
http://www.boschautoparts.com/VehiclePartFinder and search for the Bosch part number and see if by entering it at at your favorite on-line part site, yields the same part when you search by description.
The "tip" of the CPS is pointed directly at the flywheel. It is VERY hard to see on the ML. I have to get as close to the firewall as possible and looking down, barely get a glimpse of it.
On some vehicles I've heard removing the wheel and fender liner, gives you good visibility to the part but not improved access. Good luck.