I recently bought a used crossfire and assumed that it didn't have the navigation system since it was never mentioned to me in the sale. However my stereo has the "Nav" button and matches entirely in appearance to the stock nav units I've seen for sale on ebay. The only noticeable difference is that the little plastic tab in the middle of the six buttons at the top of the unit is black (between "c/c", "aud", opt" and "cd", "rad" "nav"). I was never given a navigation cd/dvd either.

Does this mean that I do have a nav system and all I need is a CD for it? I haven't been able to find any pictures of factory stereos without nav to compare it to.

 

I have the stock nav system fitted in mine and the standard one i took out.

You should not have the nav button on the stock radio.
But the black button you mention should be an LED which flashes when the unit is off.
Do you get a compass arrow on the RHS of the display when the radio is on if so you do have the Nav system.
Have a look in the menu there should be plenty of nav options which you would not have on the stock radio.