1997 Chevy Truck Wiring to trailer hook-up

My husband has had our truck (we haul cattle & horses) to the mechanics a couple of times and no one seems to be able to figure out our problem. The last time someone worked trying to fix the wiring something really got crossed. Took truck and trailer in to get wiring to work with our truck, trailer was wired wrong. When it came back, the truck and trailer seemed to work fine with each other. One day my hubby said that the cruise did not work, I had just used it the day before and worked with no problems. A week or so later we realized that we were both correct. During the day the cruise works just fine but when he was going to work in the morning in the dark with the lights on the cruise does not work. Realizing, also, that when the brake is applies the ALL of the lights come on, hense the cruise thinks that the brake is on when the lights are on. Has anyone had this kind of problem before, or does anyone have any suggestion. Maybe a wiring diagram for that part so that we can fix it ourselves, since no one else (have not taken to dealer) seems to be able to! Thanks in advance!