When my friends recently (about 2 months ago) bought a new RV from General RV, General RV told them that they do not do any work on RV's that they didn't sell. I have no way of knowing if that is true or not but you probably should call them. I would call the places on that list that Crossroads gave you, especially any that are mobile fix it types (if any). American Mobile RV repair in Pinckney comes to mind (I know nothing about them, just know of them).
If you bought it from National RV I know exactly what you are going through. While there work was OK, there ability to return phone calls is non-existant. You will have to be persistent, call 17 times in a day and leave a message, etc. You also will need to make an appointment to take it in. Your appointment will likely be in about November, and they will have it until March. Make sure you winterize it and take the battery out (ask me how I know all this). Or do whatever it take to get a mobile RV guy approved to do the work.