I looked my spoiler to double check as I recalled from washing the truck. My third brake light isn't held on by hex bolts like service instructions. It's two regular phillips screws.

If you have the spoiler and have regular screws, you might be able to save yourself the trouble of removing the spoiler to replace the light. (The whole drilling and replacing of the clips look like a royal PITA.) You'll most likely need a tool like this or this better one. I think by lowering the rear glass, there should be enough room and clearance to squeeze the ratchet tool in to get to the screws. I'm not sure if there's a socket with a low enough profile to squeeze in there if it's held in by hex nuts.