Hi Piperflyer,
Normally you take the rig to your selling dealer for warranty work and they get any necessary authorizations from Heartland or the appliance/subsystem manufacturers. If you look at the warranty statement in your trailer manual, you'll see that while the rig is warranted by Heartland, appliances and many subsystems are warranted by their respective manufacturers. Bighorn comes with a 1 year warranty, but some of the devices inside may have a longer warranty.
If you're having difficulty with your dealer, you can call Heartland Customer Service at 877-262-8032 / 574-262-8030. Have your VIN # ready. They can advise on how to proceed.