If it didn't work with 4.01 then you did something wrong cuz it works with mine.
As far as finding out if you're note button works or not try going into a game, any game, and press and hold the note button. After like 2 or 3 seconds the sound should mute.
Same as with the display button, if you press and hold it will make the screen go black.

I have a tut for installing NPR. I'll try to find it but it might not be too helpful cuz a lot of images on this site don't show up from old posts since the site was updated a couple months ago.
If I find the tut I'll edit this post one or post again.