Why would you want the lights off?
IIRC, there are two clips, one each side under the sides of the bumper, three large bolts along the "chassis" members each side underneath the car, there may be a clip under the rear, then the whole lot slides out backwards.
You have to disconnect the bumper/numberplate light as the bumper slides out.
It's usually hard to get it to move if it's never been off, wiggling/pulling and a bit of leverage from underneath all help, and if it's trashed there shouldn't be a prob with damaging it as it comes off.
The only problem you MAY have (I did) is that rear bumper damage sometimes bends the bumper fixings that slide INSIDE those "chassis" rails, causing them to bind up tight. When I clouted mine on a concrete block is was a pig to remove.
Alcazar