I installed the alpine HID's in my Z4.
http://e89.zpost.com/forums/bpgarage...o=view&id=6921
One of my ballasts had problems so Alex replaced it for me. Initially they looked very nice. 4 months later I now have an issue where the color of the bulbs is slightly mismatched when the bulbs are cold.
I thought it was the X5 kit (good idea to confirm with Alex)
It does require you to drill holes in the cap that covers the hole that allows you to access the headlight chamber. It also requires you to wire the ballasts directly to the battery. The wire provided was kinda tight, so I spliced in an extension so that I could hide the wire neatly in the existing wire harnesses.
Certainly doesn't require any specialized training to do.