Re: halogen to xenon bulbs
You really can't do just the xenon bulbs without adding ballast and proper wiring. Unless you're talking about those ebay blue bulbs where it gives you the illusion of HID? If yes, please just save your money because those will burn out quick... even the Phillips brand. If you are talking about a full HID conversion, then it will be fine. The ballast adjusts the power/voltage so there's no harm to your electrical system. You'll have beautiful bright xenon fogs (hopefully color matched to your headlights).
2012 Volkswagen CC Lux - Night blue (my daily)
2011 JGC WK2 - Blackberry Pearl (wife's daily)