If you need to get the tailgate trim off here's my method (from an unrelated issue, stopping the beeping):
"You've got to be bold! Open the tailgate. Take the small square access hatch off behind the latch. Now be careful. Pull the interior panel away until you can get a padded screwdriver or similar behind it. You then need to work your way to the left corner enough to get your fingers in. Or use two long screwdrivers. A helper might be useful. Give it a good hard wrench and it'll pop off. You can then see the square sounder with it's connector. Disconnect it. Line up the fixing studs, and thump the panel back on. I accept no liability whatsoever for any damage you might cause, it's at your risk!!!!! Silence.