I have no picture on my screen when put into reverse, I'm assuming the camera is not working. Can i purchase just the built in camera?

It's best to check all the fuses and the camera lens for covered with dirt, then follow the wire as it can get pinched near the rear door hinge and then the display can go out too. A true code scanner ( not a code reader ) can look at the body control computer and disnose this problem futher. The back door trim covers the camera and the wires are routed thought the hinge area of the rear door, the control unit is in the right rear under the trim panel and if it got wet it's though. Both of these parts are bank breakers. I recomend a dealer mechanic and ask for an estimate ... you may break good parts and or install parts that don't fix the problem oth could make you upset.. the dealers estimate could make you upset too.