I tore down entirely mine using the exact same guide (and the tools from ifixit such as the Pro Tech Toolkit, quite useful by the way). Even the keyboard was entirely torn down (I separated all layers, removed keys, their mechanism and both contact surfaces) ! So I know quite a bit about this keyboard ^^ In fact the keyboard and power button are on the same connector. The fact your backlight is functioning is normal : it is plugged on another connector as you can see in the guide.
Personnaly, I think the same : your keyboard is either disconnected or dead. Reaching the keyboard is not hard, just very long. If you are and stay patient, follow the guide, there is absolutely no problem, weather or not you are a skilled man ^^
If you still is scared about the idea, you'll have to find a way to send it to Apple