Min thickness is 7.3mm.
My 97 C280 with no ASR does not have any wear sensors on the rear, but I believe some models might, check on your car to see of there are any.
No allen bolts for the pads, it is a fixed caliper on the rear. Hammer out the cross pins with a punch and pull the pads out. Then unbolt the caliper of you are changing the rotors too.
Make sure the parking brake is off when you pull the rotors off.
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record