Thanks to all who replied.
I had decided to park the problem till after the holidays. Next week I plan to call around to see if I can find a mobile mechanic who'll trek up here from Las Vegas to diagnose & fix the problem. If that doesn't wash, will have to work on getting the rig towed down to the Cummins dealer.
As to airing up, there's a standard male air fitting in the rear of the engine compartment. I've used it for airing up tires and doing a quick air dump. Seems I could connect a hose from my big NAPA compressor and pressurize brakes and suspension. Any problems with doing that?