Although not standard on all trim levels, I thought you could get the camera without the NAV, but I might be wrong.
Ask the seller if it has one, it is very obvious when driving/reversing the car... or look at a picture of the trunk area. It might be poking on the driver side under the top chrome trim.
I know I've seen older cars with aftermarket backup cameras so I figured they have some sort of module that is triggered by the car's reverse signal and displayed on an aftermarket headunit (I don't know of many, if any, aftermarket headunit installations in this platform). No experience with them personally, but this picture is all that is involved in an OEM system:
