L.E.D. lights are cool, shouldn't need to look for any red flags. They're brighter, last longer, won't mess with the turn signal flasher near as much, they're the way to go.
The big round trailer plugs are all wired the same (assuming it's wired at the factory) and I've included a pic in this post that show's what is where in that plug. The diagram is showing you the truck's side of the plug looking at the pins of the plug. You'll notice there is a reverse light wire in there already. So if you wire up your trailer using that big round plug you'll have your reverse light capability pretty easily.
The 4 pin plug is the most common. The pic of the 4 pin plug is the trailer side of that plug.
Trailer wires (never varies if factory wired, either style of plug):
White: ground
Brown: tailights
Green: Right turn signal/brake light
Yellow: Laft turn signal/brake lights
I recomend running all of the various light ground wires to the tongue of the trailer, grounding them all at the tongue in the same screw, and wiring up the trailer's plug's ground wire to that same screw so that they are all grounded at the exact same spot. I also recomend using a small bolt and nut for the ground wires vs. a self-tapping type of screw.
Hope I helped and let me know if I missed something/you have a question.
