Australian Car Repair Issues? Ask an Auto Mechanic for Answers ASAP
If you remove the trim at the rear edge of the roof when opening the tailgate, you should have enough access to get to it. You will need to unplug the antenna before removing the nut. I would guess that the metal may be tweaked slightly, so it may be better to take it off all the way, see what you can do to straighten the panel, then re-install the antenna.