If this a Chevy chassis, Norm is probably right. I'm surprised to hear that it's a Class C instead of a Class A, however. One way to disengage it TEMPORARILY without things going BOING is to tighten the Locknut on the Actuator Shaft against the housing, then continue to turn it until it pulls the Shaft out enough to disengage the Brake. You might need to use a fender shim of the right size as a washer if the hole is too big for the Locknut to seat against it. As Norm said, take all precautions so the MH doesn't roll over you.
Above all, get in touch with Oldusedbear before you let anyone touch it, as Norm said.
Please keep us posted.