If your signature info is correct and you have a 2002 the electronics could be different from other years, maybe one of the site electronic gurus will answer soon. But overall I think you could buy an in dash head unit with monitor and backup camera from a place like www.crutchfield.com and they could set you up with the correct harness needed for your app.
As far as running all the time with a camera on you may get blinded by headlights on the road at night and that could be distracting as well a negate the usefulness of the camera. Otherwise you may need to develop good mirror skills and act like a semi truck driver and just be aware of blind spots.