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.