It is a simple setup made complicated by pre-wired socket. The important part of "pre-wire" is that the 12 volt supply is available at the mounting location. I assume your new camera is wireless. Most now days are.
The wire behind the mount is probably connected to either backup lights or marker lights. Mine is connected to marker lights.
Cut existing socket cable at the wire nuts. Connect your camera at that point. Be sure to use automotive wire nuts or splices. Vibration tends to disconnect home twist on wire nuts.
Adapt mounting plate as needed.
I wish you good luck and happy trails ahead!