How does this trim come off.

[rs74]

I am trying to get the corner bed trim off. I took out the tail lights and can see a clip towards the inside of the bed and a nut towards the outside. The nut is just spinning and seems like I am getting nowhere. Does the nut have to come off first. I was going to try and get it off the clip to be able to put some pressure on the nut to see if it would help get off. Can these be bought aftermarket. I am scrapping the bed and was wanting to keep them. The rest it looks like it just stick on trim and this is the only pieces that actually bolt on.