I put HID in my 2003. Not sure if the headlights are the same for your year. The entire assembly slides out easily once you know how to release the securing ring.
I had to drill a large hole in the plastic cover that snaps on the back of the headlight for wires to pass through. Cannot recall the size, 5/8 or 3/4?? Uses a flat paddle bit and this was correct for the grommet to fit the hole that was on the ballast.
I mounted the ballast inside the frame rail opening, high behind the headlights. Used adhesive Velco on the ballasts to keep them mounted in the frame rail openings.
You will also need to use a relay harness for the HID ballast.
I ran without one for a while, but it is much better to install one. Not a hard job, just takes some time.
Also I have been unhappy with the bulbs that I have been getting from DDM Tuning lately. They are cheap, but they use Chinese crap. Had a few problems with bulbs and also light pattern due to bulbs. I had purchased a number of kids years ago that worked great. Finally had a bulb go after 4 years in my truck. But given I was going through Silver Star Ultras in my truck every 6 months for close to or over $40 a pair, the $45 HID conversion that had bulbs that lasted for over 4 years was a good investment!