You can do all that. But to make life easier, and just as good, get an aftermarket camera, mount it under your applique just like the factory one, and run the wires. Its not worth pulling the harness because it ties into the whole liftgate harness. You can use a factory camera without a camera module, you just need the pinouts, which I have.
For the nav unit itself, you'll need the brown plug (again, which I have) and the GPS antenna. It will then need to be programmed at the dealer to unlock the VIN. Keep in mind - yours is a 2007. In 2010 they added USB, and in 2012 they upgraded to a hard drive for navigation and music storage. 2007-2009 can easily be unlocked at the dealer. Most dealers have a very hard time unlocking a 2010+ USB radio for 2007-2009 trucks, and it requires special programming. Greg at CPS Audio can do it for you for a small fee (and shipping to/from). Hes done several for me and other members on here.
If you go 2012 radio upgrade, the complete radio harness is different, as is the usb connector and XM antenna connector. Harness kits are available though.
Or you can go aftermarket with a unit, dash kit, harness, possibly save some money, and have close to the same features if not a bit more. It just wont look factory.
Hope this helps.