Now that you can see the back of the individual keys, stop there.

You now need to unscrew the 2 small, black Philips screws from the back of the power button assembly. Failing to do this will tear the the power button's ribbon cable when you try to remove the keyboard.

After you do this, remove the power button by pressing on the power button from the top of the upper case. The power button and a small metal ring (spring) will come out.