I love St Anger. It's one of the most honest things they've ever made. However, like any Metallica post '92, it's far too long and could happily lose two or three songs.
It does sound horrible, but it's supposed to.
It's a primal scream.
Look at that! That's really something, nice one.
I'd vote for leaving the neck as it is, the bass has a classy understated thing going on right now. Black triangles would be a bit too much I reckon.