wtf. diagram? Its not difficult. open the damn bonnet and aim for the back of the big shiny thing with clear plastic at the front that makes light
theres 2 black plastic boxes, the nearest one to center is for main beam. the dipped sides are far over to the corner. remove box. unclip bulb, remove bulb, then reverse to re-fit.
a torch might be requrired to see what your doing but thats it.