Jeep Hitch Plug

Hey everyone, I'm wondering how much a hitch will cost and how tough it would be to install it on my own (my dad can probably help me out, he's really good with this kind of stuff and I'm sure he knows how to do it). Still, I'm wondering how much the hitch would be. I'm getting a new car, and it already has the, I don't know the technical terms, but the receptacle for the hitch and I think the plug for wires as well. Because I don't know the terms, here's a link that shows pictures (you can select a few of the back end, sorry I don't know how to make it link directly to them): http://www.carolinachryslerjeepdodge.net/new/Jeep/2011-Jeep-Liberty-e599018a0a0a00640123a08e9cc1e35b.htm

So the receptacle and plug are already there, I'm just wondering how much it would cost and how difficult it is to install the hitch on your own. Thanks a ton for taking the time to look and answer!