Underhood Wiring problems of the 2000 Chevrolet C/k 3500

After towing a trailer, the rear tail light bulbs blew out, they were replaced and blew again along with a main relay fuse under the hood (never small fuse from dash fuse box). After replacing that twice we continued to have a problem, the vehicle was under warranty so we took it to the dealer, they said it was shorting out because of a bare wire and they fixed with black tape(still have not located that wire) the warranty expired shortly after and the mechanic did not do an invoice for electrical tape. . . Since then we have continued to have numerous problems with the electrical system including the rear tail lights, brake lights, rear turn signal lights, passenger power window control, parental window lock control, hazard lights. We have also had to replace the battery 3 times in just over a year. We had an electric brake system installed at the time of purchase and have checked that wiring and the trailer wiring for bare wire shorts and found nothing. We no longer use the trailer lights so it is not an overload?? any information on possible defects would be appreciated.