I think you need the Kenwood stereo keys. 1st MP3 said that they are supposed to come with the Kenwood owner's manual thing, but I don't remember getting any (or I lost them ). Either way, I am trying to figure out where I can get some so that I can take out the box thing underneath the head unit.
I don't have the book in front of me, but I remember there being two keys you need. One was a U shaped thing the second was a hook thing. I'll check the book in the morning when I go to my car, think it says the ones you need.
Edit: You need Accessory 8 Removal tool and Accessory 2 Removal tool. Use #8 on the top and bottom first near the corners, then # 2 on the sides, it shows using 2 at the same time. Also, it's on page 41 in the Kenwood manual.
Use butter knives, they should be small enough to fit in the sides. if not just find something small, flat and metal that you can stick in the sides of that puppy. You don't necessarily need "Kenwood" keys, I uses my "keys" from my Pioneer decks.