I have an R/T without the Tow kit because I am going to put my own on. If you look at bch's photo above if you want it to look stock you will need the receiver bezel. Dodgeparts.com has it and you can also order it from your dealer. Its only $26.00.
You will need to do trimming/cutting to your bumper cover. Below is a link:
Dodge Nitro Receiver Bezel
As far as aftermarket hitches Valley Industries, Hidden Hitch, Draw Tite and Curt all make hitches thus far. The best prices I have found has been etrailer.com. Below is a link directly to the Nitro page... don't forget you will need a wiring harness also. The links for the harness are to the left of the hitches on the same page.
eTrailer.com Nitro Hitches
Except for the trimming of the bumper cover, installation is a breeze for anyone who is handy. Most hitches use existing holes on the frame and should only take a short amount of time to get bolted up. I hope this helps you guys out.
-Lil'