I just did something similar with my truck, here's the thread relating to the topic.
Gentex backup camera monitor with pre-wired harness
In case you're wondering which wire does what on the camera harness in the tailgate, there are 4 wires going into it. Red and black as usual are the power inputs, red being positive and black the ground. The two other wires are the video output. If you've wired up the monitor and receive a garbled video signal, just switch the two video wires and the image should clear up. If not, there must be some other type of interference or video incompatibility.
Keep in mind that the camera requires the 5.5-7V power input to come from the connector in the overhead console. Whatever head unit you get to go with the camera, look to see if it is able to provide the correct voltage to the camera. If not, it is a relatively simple task to use a higher voltage signal and tie in a voltage regulator to drop it down to the required voltage (the fine folk over at Digi-Key will be willing to help find one for you).