The RV Camper.ComEverything RV!

I just got back from the Uhaul store, I purchased the whole deal for a trailer hitch (tongue, ball, pin, wire kit). The prices were reasonable till the guy looked up on the computer and told me I needed a rough wiring kit with a power module because my Chrysler Pacifica tail lights would not supply enough power to the trailer lights. So basically I have to run a wire all the way to the battery then to a power module that goes to the car lights and trailer lights. Just want to make sure I really need to do it like this or if a cheap wiring kit from Walmart or something that hooks to the tail lights would work.