First off, I want to welcome you to NICOclub. I really hope you enjoy the Murano forum, and find it informative as well.
Now, some help on your issues....
1. I am a bit shocked that the AWD button let loose, I am guessing that maybe a part of the plastic that holds the switch in place, I personally have never taken a switch out, but you can check out the service manual for free at the following link:
http://www.nicoclub.com/FSM/
2. Maybe try replacing the fuse, also on my Armada there are addition fuses under the hood, I am not sure if that is the case on your Murano, but it maybe worth checking. You could also call a Nissan dealer and see what their thought might be on that. They can't charge you for a phone call!!!
Good luck and let us know how things work out!