It depends. Installation is a little more involved if you want to install the power cable directly to the car's fusebox. Alternatively, just push the power plug into the cigarette lighter or a similar auxiliary socket. Once I had decided where about on the windshield I wanted to position it, it took me no more than 15 minutes to install. Of the cars I have fitted them to, Ive only had one fall off. I put that down to trying to stick it to the windshield when it was cold. I just ended up running the car for a while with the demister on until it took the chill off.
As for positioning the power cable, that seemed easy enough. I run the cable along the front edge of the headliner -- tucking it behind the headliner so it can't be seen. Then run the cable down the 'A' Pillar -- tucking it between the 'A' Piller garnish and the seal. Some cameras come with a spatula for that very purpose. Then I ran the cable down under the dash and out to the cigarette lighter at the front of the centre console.
My camera is the next model up from this one. The person in this video installed his pretty much the same way I did. The only thing I did differently, was to position the camera higher up, so that the body of the camera is on the 'dotted' area, with the camera lens protruding just below the dotted area:
