Some time ago I remember reading here about cautions re: correct factory wiring for trailer hook ups. As I recall there was a relay necessary to pevent burning up headlight switch. I have a '97 3500/cummins. I discovered the truck did not have the factory towing package. Having just replaced the headlight switch. I would like to not repeat the effort. Can someone refresh my memory with respect to trailer wiring. I would like to go with a 7 pin rv pigtail. I stopped at my local dealership for help. I was greeted with a blank look. Not the level of help I expected from a professional. Thanks in advance.