As far as i know this is not a cheap mod at all. I wondered about this when I was looking for a 250 how much it would cost as there were barely any with xenons at the time and all seemed to have halogens. For starters the units are atleast 300 a pop. Also think i seen that the correct wiring is not there if you just have the halogens, like for the ballasts etc? Why i searched so long for one specced with xenons and cup chassis in the end.
Speaking from doing the conversion on a 225, it is far from a straight swap of the headlight units (if you want to do it properly..). The headlight wiring loom will need changing, as the connectors are more than likely different between the headlights, but on top of that, you'll need axle height sensors and headlight washers plumbing in. You'll then need someone handy with a CLiP to enable discharge lamps, and then calibrate the headlights with the readings from the axle sensors. It wasn't fun, nor cheap, but worth it!
Well from what I've read so far there are the same connections but you need some kind of invertor for the pulsing issue, this is enough to make them work but yeah you still have the auto'leveling stuff that won't work without a lot of work. My car despite not having Xenons does have the headlight washers, and they work! (as i found out yesterday)
all RS mk3's have headlight washers, afaik.. the ballasts are built into each headlamp, but there is an additional 'headlight control unit', and how/if it affects the light itself or just the beam adjust up/down/sideways, I'm not sure, but the power input to the headlamp for the xenon beam is definitely not just a regular dc signal, but some sort of pulsed business (still 12V though)...
