my backup lights stopped working. how do I replace them? and what is the parts model # for the back-up lights?

Both of them at once? It's probably a switch.

 

You get to the bulbs through the trunk (open the trunk, on the back side of the lights there will be some covers and behind the covers are the wiring harness/socket things).

Take out the bulbs and check them for continuity. If there is continuity, they're not burned out. If there isn't, then replace them. If the bulb type isn't marked on the base of the bulb, then look up your vehicle at http://www.sylvania.com/ConsumerProducts/AutomotiveLighting/LampReplacementGuide/ .