2002 silverado trailer brakes setup

Iam new to the trailer brake thing, My truck has factory wireing , looks to be 5 prong , Iam buying a brand new trailer with trailer brakes, they said I still need to do some wiring and put some kind of box in the truck.
is this true?? I was under the understanding, it was all there from the factory??

I just went through all of this for my '99. There's some good info at etrailer.com; specifically, have a look at: http://www.etrailer.com/faq-cbc.aspx
If the link doesn't work, go to the brake controllers page, go to the commonly asked questions link at the top, the go to the installation guide at the bottom of that page.

For my truck, I had to connect the wires at the power box under the hood, and run a pair of wires back for the trailer brakes and the aux 12volt in the plug. The other wires for the lights are all in the back harness near the spare tire.

Installing the controller under the dash was probably the easiest part; running the wires back and hooking up the connector plug was a bit more effort, but in all, I'd say it took a couple of hours.

Thank you, looks like from what the site says on the 2002, I dont need alot.
thank you for your reply.