I don't see why you should replace the rotors if they are not worn out. My light came on this week and I changed the front pads on my 85 300td in about 40 minutes. Pads and two sensors cost $35.
Pull the wheel. drive out the pins that hold the pads in place with a hammer and nail, removing the tensioning spring, disconnect sensor wires, pry caliper pistons back by using a screwdriver between rotor and old pads, put lubricant on back of new pads, install.
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13