While I am awaiting the arrival of the upgraded, LED headlight, I removed the stock HS1 bulb, and installed a brighter, H4 bulb in my RX3's headlight. I am very pleased with the light pattern, and the extra illumination the H4 bulb projects on the road ahead.
Here are the steps I followed to change the bulb.
Slightly loosen all the windshield bolts, so you can tilt the windshield slightly for some clearance with the headlight. EDIT: This might not be necessary, if you are willing to wiggle the headlight a little to coax it out from behind the windshield.
Remove the two bolts at the side of the headlight. Note the alignment of the headlight with the bracket; this will affect the elevation of the light beams.
Pull the headlight assembly out from underneath the windshield.
Holding the headlight assembly so it does not fall, disconnect the wiring plug by pressing
down on the tab.
Remove the nine bolts from the back of the headlight assembly, and open the headlight assembly.
Remove the plug from the bulb.
Remove the rubber boot surrounding the bulb.
Twist the the bulb retainer counter-clockwise, and remove it.
Remove the HS1 bulb.
Install the H4 bulb. It might be necessary to flatten two small projections on the mounting plate of the bulb to allow the bulb to sit flat against the mounting plate of the headlight.
Repeat all of the above steps in the reverse order to re-install the headlight.
I borrowed the disassembled headlight photograph from Katflap. Thanks, mate.