If as you have tested and found the external keyboard works, DT&T Services can sell you the keyboard for the computer for about $195 installed or you can call them and they can send you the keyboard for a bit less and you install. I had to replace the keyboard from a 15" Macbook Pro from Aug 2010 and other than having to gut the entire computer to get to it there was no problems. See the following link:
http://www.dttservice.com/macbookprounibody.html