I have been doing the samething. Only issue I realized is that if you have fog lights... you are going to need to change them as well. HID or even Xenon light kits will make your headlights brighter than you fogs.
Also there are people who make conversion kits. Prety much just a bolt on system to your original headlight system. Last I heard from a friend they are about 250 a pair. Same guy was able to do fog light conversion as well.