They come in kits, from $300 to $400 usually. The install is fairly straight forward, but it's a bit difficult to get access to the area you have to work in. Most say it's not all that hard though.
You can do a google search or search Ebay for H11 HID conversion kits. If you can find one with compact ballast, that's going to help in finding a place to install them under the hood. I'm partial to the Mtec kit, although I haven't bought one yet.
http://stores.ebay.com/mtecpower_4500K-MTE...7QQftidZ2QQtZkm