Call customer service and make an appointment with Factory Service. The service area is separate from the factory.
Your appointment will be for a Monday morning at 7:00am. Many people arrive the Sunday before and camp there--there are spots to plugin. At 7:00 am on Monday a tech knocks on your door. They pull your unit into the shop and you can either wait in their waiting room, rent a car and go somewhere (tour a plant, visit the RV hall-of-fame nearby, etc.). Around 3pm ish they will return your RV to where you parked it (or before if the work is done). If more work is needed you spend the night and at 7:00am the next morning they are knocking on your door again...
They are pretty booked up so your appointment will likely be 3 or more months out.
In the waiting area they have a binder that lists all
of the RV plants that offer tours (not just the Thor ones), what days the tours are on, and where they are.
Camping at Thor:
The waiting area: