Yes you could just tap into those two wires. You will also probably have to tap into your reverse wire to send that signal to your head unit. That way you can set it to automatically come on when in reverse. The stock camera is always on but the mirror is activated by the reverse signal. So if your head unit allows, you will be able to view your reverse camera view at any time, not just when in reverse.

The video + and video - wires are both white coming out of the camera. I am not sure but I would assume that they would be the same color at the mirror. If you want to strip them back, the video + has a copper colored core and the video - has a silver colored core.

The reverse wire is located at the mirror as well or it is located under the passenger door sill plate in the massive group of wires there. The reverse wire is green/brown and will show 12V when the vehicle is in reverse only. There are 2 identical green/brown wires in the bundle. I'm assuming 1 goes to each of the backup lamps but I'm not certain so make sure you test before you install.