Thanks! Do you have the name of the backup camera you got?I installed a Pioneer AVH-X8500BHS DVD receiver in my car few months back and love it! Last month I installed a $15 back up camera from amazon and it's been great. Good reviews, great price, has grid/guide lines, I couldn't be happier.
And to answer your question, no it doesn't have to be a pioneer camera. My car is at the dealer. I'll post some pics tomorrow when I get it back tomorrow.
Heres a link to the camera.
Amazon.com: HDE E336 Waterproof Rear Vehicle Backup Camera With 170 degree Viewing Angle: Car Electronics
No you do not have to replace the stock head unit.
You can go a few ways but I would do this if I were you...
Replace your stock rearview mirror with the Homelink/LCD screen from Gentex (google for model number, pricing is about 3-500)
Get the proper trim piece and camera for the trunk and install.
Connect the camera to the mirror (IIRC it is a simple RCA plug for the signal input to the mirror)
Looks way better than an aftermarket LCD screen on/in the dash and you keep the stock radio.
Or look at the other solutions from vendors here on the forums that replace the factory radio face.