My 95 S320 will need new pads and rotors this spring so I'll be interested to see how it works out for you. I've done the brake pads on the front and this is incredibly easy. I think the pads on the rear will be the same. I believe the only trick to changing the rotors is to remove the small countersunk hex screw and be sure the parking brake is released. Not having a repair manual for the W140 sucks. Maybe someday MB will release this info. Good luck.
1984 300D Euro