After nearly a week, our brake saga is now over. Not only do we have a completely new parking brake system, we have now replaced all the service brake "stuff" associated with the drive axle. I took Gerald's advice and had the brake lines replaced. The old ones were hard and brittle and we all agreed that they could easily have caused the rear wheel lockup we experienced last summer. Fortunately, the calipers were only ~$93 each at NAPA and the rotors were twice that, but all in all, the overall cost was tolerable. The brake line fabrication was $100 each.
I should say that the coach now brakes better than it has in the entire time we've owned it. It's much easier to modulate the pedal pressure; previously the brakes had exhibited more of an on/off behavior, which was heightened after last summer's overheating.
