I PM'ed you the guy's email and phone #. Have you checked out the dieselgiant write-up regarding the glow plug
system?..
http://dieselgiant.com/glowplugrepair.htm
does your car have the same set-up as the one shown? Or does it have the relay mentioned in this pictorial?
http://dieselgiant.com/mercedesdieselloopglowplugrepair.htm