I almost bought a new phone after my shift key stuck. I went to look at the 680s, and was about to buy one, but figured I would give this a try first.
The instructions above are nearly flawless. The only thing I did differently was that I only pried up the tape (it didn't look like foil) on the shift key a little bit -- not even enough to look under it. After I pried it up a little, it responded like the other keys; it would 'pop' a little bit when I pushed on the pad.
Also, for anyone who is interested, there's a "how-to" at:
http://www.geardiary.com/2006/12/30/...-instructions/
Although it's not specifically for changing or repairing keyboards, it shows pictures of the disassembly process, and gives more detailed info on how to separate the two halves of the phone for those of us without any computer repair experience.