1)
#/f/showthread.php?t...elease+install
see step 10 onwards
edit: i believe that third smaller ring is for smaller diameter horns so they sit tight inside the qr cavity (or perhaps a spacer of some kind). one came in both my cheapo egay qr and the wb one i have now. my horn is too big for it so i've never had occasion to use it, so i can't be sure.
2) no idea on a s13. if the control is on the steering wheel like the s14, then yes of course.
3) for wiring see link above. as for whether the horn will fit in the quick release itself, that depends.