Mike,
Everything I have heard points to replacing the rotors when they get too worn or warped instead of just "turning" them. I'd stick with OEM pads, nobody who ever runs stock pads complains about the braking performance! Aftermarket pads have a bevy of nasty side effects. You might improve one area but you will sacrifice another. (less dust...more noise, longer pad life....shorter rotor/caliper life, etc) BTW Jurid does alot of OEM pads for Mercedes. Sort of like Behr radiators... If the rotors are only very mildly out of true then the pads will "adapt" themselves to the shape in about a week or so. Its hard to say how much rotor you have left...(do you have any measurements?) If you still have a good amount left or they are not warped then just let the pads break-in to the rotor contour. If you need any help check out our DIY article. It specifically shows W124 M119 4.2 V8 brakepad change.

Happy Motoring....Lee