I don't know how Cummins Southern Plains hourly shop rates compare to your dealer's. I would think the Cummins guys, due to their specialized expertise, could get the problem repaired in fewer shop hours than your dealer, though, so it could wind up being cheaper at Cummins. I guess you'd have to get a firm quote from both to be sure, but until the problem is identified, you'd be hard pressed to do that.
Rusty