I was in a hurry and probably wouldn't have normally spent the money otherwise, but I went to CW and pulled whatever plug n play adapter they had on the shelf. I think it was a Hopkins all-in-one kit. It basically plugs into the existing harness, leaving the outlet at the hitch open for your trailer, if you have the need. Fairly easy to install. On my truck, undoing the dirty mess at the back of the harness was the most work. Once plugged in, from there, was just a matter of routing the 12' or 13' feet of harness to the front of the bed and selecting an area to drill for the outlet. Sprayed some jiggle can truck, "bed liner" around the hole edges to prevent rusting, drilled holes for outlet and mounted it. Done.
Would I pay $80 again and do it the same way? Probably not, but I'm cheap too. The kit made it pretty darn easy, I will admit.
I'd buy the bundled wiring and plugs/outlet separately. I'm pretty sure that bundled 7 wire trailer harness by the foot, at Lowes, or Home depot is some where around a little over a $1 per foot. At 12', that's a whole lot cheaper.