I'm trying to put a player-run shop in my game, but I'm trying to figure out the best way to display what the person is selling, I'm putting all the items into a list, after the items have been assigned a price, however, I'm not sure how to display the items whenever the player is clicked on...

Should I create an info box for it? Or maybe a browser? Pretty sure output wouldn't work, but I don't know for sure.
You could use a grid or a statpanel().
You could use a grid, or you could even use a browser with some HTML/Javascript.