[Warning Light] Reverse sensors

[Colr6]

Hi new to the forum and new to berlingo ownership. Just tidying up my berlingo van and the rear bumper needs replacement. So is there to much involved in fitting reverse distance sensors ? I was thinking of going to the breakers for a bumper and wondered what else I would need to complete the installation. The van is a 62 b9. Any help would be appreciated.
More info.
 On the interior light there are three lights, the outer ones are not wired up so don’t work. On inspection there is a spare wire up there but doesn’t fit either of the terminals on the light unit. Again is this a simple fix or is it run a feed up there from a perm live.
Thanks in advance Col.

[Sol]

For the factory sensors, there's an ECU dedicated to that mounted in the rear side panel in the boot area and it connects to the factory stereo and multi function display to show parking distance to objects at the rear and to the sides of the rear. The beeps for distance change with approach to an object and come through the stereo.