Tailgate camera in 2006 tacoma?

New to the forum, please bear with me! So I've been searching the forums and got some great ideas so I guess I'll start from the beginning: I own a 2006 tacoma and bought a new tailgate with an OEM camera a while back. I just bought a new head unit and thought now would be a good time to hook up the camera. Since my truck has no wiring for the camera, or the harness that goes into the existing camera, I figure ill use a molex connector to make things cheaper and just run the wires from the tailgate to the HU myself. I plan on tapping into the reverse light for camera power and also for the reverse signal wire so when I shift into reverse the screen should pop up with the reverse camera.
So my questions are: how can I wire the HU to play DVDs while driving? I read somewhere I can ground the wire for the parking break signal and that should do it. (The head unit is a jvc kW-NSX600)
How can I wire the video positive and negative wires from the molex connector to an RCA cable? Can I take an old RCA cable from around my house and splice right into that? (I think the positive is usually the middle wire and the negative is the outer case)

Lastly, I was hoping to add some sort of toggle switch that would allow me to turn the camera on and bring it in on the screen WITHOUT being in reverse. As well as it automatically popping up when I do shift into reverse. (Just thought it'd be kinda nifty to have that option). Anybody have any ideas on how to pull that off?
Any help and/or good ideas appreciated! And thanks in advance =)

 

Check Amazon or Ebay for a microbypass for watching video while driving. I use a switch for my camera so I can switch it on at anytime as you suggested, but I don't run power through the backup lights. My camera came with all of the leads so it was easy to wire up...just like wiring up aux lights.