The bearings and races are inside the wheel hub which the rotor bolts to. You definitely won't get new races with the rotors. The brakes on a 1st generation w126 are exactly the same as the ones on a w123. The only difference is that the front rotors on a 126 are vented and the caliper has a shorter piston to accommodate the thicker rotor.
I put the rotors and calipers from a 126 on my 300TD.
I don't know of any trick to get the bearing seals off without ruining them.
Leave your races in the hub, clean out the hub thoroughly once you get the new rotors bolted to them (with blue loc-tite on the bolts), and then repack the bearings with fresh grease.
