Bulbs are 501's.

On my old ST170, it was just as easy to remove the lights to do any of the bulbs, mine had 2 bolts but IIRC theres actually 3.

Theres 2 bolts and 2 clips to remove the grille which you'll need to take out to get the lamps out, one bolt on the top of each and one into the wing. Not sure exactly where the 3rd one is buti'll try find out exactly where it is now.

EDIT: Seems like there is another bolt underneath the headlamp apparently, mines never had that one though.