If you pull up the speaker grills and the carpet on the tray you'll see 4 (I think, it's been awhile) nuts that hold the box to the tray. Undo those nuts and the box will fall down, literally. As for the metal tray itself, it's welded in at the factory.
You need to take out one of the coat hanger hooks from the back then pull out that triangle trim piece abit from infront of the seat belt spool. Then take flip down the seats, take out the bolts that hold on the trim piece and then pull it out. Then you can pull out the cardboard type piece with the speaker grills on it (you will have to bend it a tad) to expose the nuts that hold on the speaker box. Then go into the trunk, unplug all the wires from the box and support it with a box or a friend (it weighs about 25 pounds) and then undo the nuts and lower it down and pull it out.
Fun huh?