The only part you need is the actual HID kit. Bought it from theretrofitsource.com, same site I mentioned above. I also commented on the performance above. No flickering or issues turning on, been perfect since day one.
I spoke to the retrofit source a few weeks ago to inquire. Gave them the model and year and they asked me for a part number for my existing lights, which I didn't have. I was surprised they would need that info. I assume whoever I spoke to was misinformed. I'll try again.