I took mine off last week to access the tailgate brakelight. Once you have removed the two screws - one each side where the cover catch is, the 4 panels are all held with plastic trim clips. I found that with a bit of gentle persuasion they just popped off. You have to do the panels in the right order because of the overlaps. The top panel ( nearest the roof) also has 4 slots that slide out.
I did the Heath Robinson version as didnt want to break any plastics and masked the edges and a small squirt of black silicon sealant and all quiet now. Silicon will peel apart easy enough and didnt use hardly any.