http://www.pirate4x4.com/tech/billav.../tech/Prodigy/
With the factory tow package, your life is easy. Personally, I would buy a brake controller and a pigtail and ditch the factory pigtail you have. That way, you can just plug the new pigtail in under the dash, plug controller into pigtail, and put the fuse in the box.
If you go to etrailer, you can put in your vehicle info and they will match you up with controllers and harnesses. I used a Curt proportional controller, it is a nice unit and easy to set up.