Check out hidplanet.com, they have a wealth of information.
You could do it the quick and sloppy way like me, just open the headlights, cut off the back, and eyeball what looks about right, then drill some holes and screw the projos in. Then just cover up the projector with whatever suits you. There is a great thread on HIDplanet for ideas for materials.
There is a better way of attaching the projos that will allow you to test and adjust the aim of the projectors as you find you need to. I think JnC has a post over there showing how to do it.
Really, everything you need to know is there. How much effort it takes is up to you and the quality you need.

I didn't know "theretrofitsource" is selling those kits now, that's pretty cool. But you can easily piece together comparable sets for a lot cheaper. HIDplanet has a buy/sell section where you can usually find stuff for good prices.
If money isn't much of an issue and you are willing to pay for time and effort saved, those "theretrofitsource" kits look like a good way to go.

I know there are people/business that will put together your retrofit for you, but obviously they charge you.

 

HID Planet has been a huge help to me, to say the least... Surfing around over there helped me make up my mind what I want to do with my headlights. Unfortunately, money's tight so it could be awhile, but we'll see...

While TRS does charge more, they're local to me. That's why I'm looking into them. I like to support local businesses even if it costs me a bit more...

 

Man I had big ideas for headlights, but I knew I would never find the time to do everything I wanted to do. I hope you follow through with whatever you have planned.

 

You don't mount them to the housing, you mount them to the reflector so that you can still adjust them like normal headlights, getting a spare set of headlights is the key, cuz you can take your time and not have to rush to get your car back together. I pieced my kit together with all OEM parts, I didn't use any kits either.

 

You gotz PM...