Penetrating oil fixed the stuck rotor problem. Yes, it was necessary to remove the caliber carrier that is held by two 19mm bolts. I needed a breaker bar to loosen the bolts
The second wheel was lots easier. I applied penetrating oil to the rotor's mating circumference and removed the caliber carrier first. This proved good access to the rotor and, after removal of the disk set screw, the rotor came off with one good whack from the hammer.
An acquaintance from work tells me that he just paid more than $700 for a dealer to replace rear pads and rotors on a MY 2000 C230. I feel pretty good.