blackfox is right. The ebay hid kits are designed to just replace your stock 9004 bulb. The stock housing is NOT made for HID's. It will produce a lot of glare and oncoming drivers will not like it at all. A real HID kit with ballasts and ignitors runs at a lower power level then halogen lights and will not roast your harness. The only issue might be with intial start up of the ballasts. It pulls 4x the current (13 amps) during the first 5 seconds when the bulbs are warming up, but only uses 3 during use. That could be dangerous for the harness and relays should be used.
I used to have an ebay kit on my car and there was glare but i never got flashed. Only once or twice when going over a hill. Starscream put a jaguar setup in his car and his pics looked real good. You could talk to him for more info as well.
The right way to do it is with projectors. I'm retrofitting a pair of bmw 330i bi-xenon projectors into my stock housings. This way there is no glare, i get amazing light coverage, and I still get to use high beams. I'm just worried about the projectors being seen too much and looking ricey.