There once was a robot named Lloyd
Whose mobile devices all had Android
He gave a Nexus 7
To a good boy named Kevin
And the tablet was thoroughly enjoyed
I recommende purging all data and cache for Google Music, and removing the account you're signed into for the application. If you can see the music you just uploaded on another Android device, then it is something with your Nexus 7's settings.
Google Navigation is just a separate launcher icon that comes with the Google Maps application (which is standard on Nexus devices). Not sure what you're expecting, but Google Navigation is a standard GPS navigation application.