It sounds like the same setup we have. The little on/off lever on the thermostat is VERY stiff, but it will move from the off to the on position. I was afraid ours might break the first time I used it, but it survived. It has remained stiff for the 10 years we've owned the Airstream. This isn't a guarantee yours won't snap off.... just sharing my experience. My best guess is that you'll be just fine moving the little lever.
2002 22' CCD
2008 Dodge Ram 1500 5.7L Hemi