If you still have the original Miller headlight rim, there is a single retaining screw underneath the headlamp. Undo this screw, pull the bottom of the rim forward, then un-hook it from the top of the nacelle. This screw should have a short spring on it - to make it possible to adjust the height of the headlight beam. If all the lights appear to be dim, make sure you have a good earth - a faulty earth will result in that connection being made through other units (effectively halving the available voltage). A quick check can be made with a length of flex to connect the shell of the headlight unit with the engine crankcase - if you have a poor earth, the extra wire will vastly improve the light output. When I rebuilt my Dragonfly, I included an extra earth wire in the loom to guard against such problems (they can often be traced to the use of 2 pack paint - it is a much better insulator than the old Cellulose paint!).
Regards,
Eddie.
