okay, here's goes my $2.00 regarding projector housings.
Yes, you may just stick a pair of projectors inside a headlamp, but the real problem is having them aligned so that the beam are even, instead of looking like The Rock when he does his eyebrow thing.
Yes, you'll lose your high beam when you decide to put projectors inside the housing, unless you put in high beam projectors. I doubt both will fit in one housing. Also, splicing the existing wires to make two different connectors will be quite a task. Chances are good that you'll lose your high-beam when you put in an HID kit anyway, unless you get a dual-beam HID kit.
Lastly, if you guys, and gals of course, want to tamper with the idea of projector housing, a heat gun will definately go a long way in prying the lense off the housing.
There are various complications that come along with a project like this, so be prepared for anything. It's not quite as easy as it looks, but of course we all knew that right?
Oh yeah, one last thing for those who want to take on this task, make sure to have another lamp handy since you wouldn't be caught in a predicament where you've chopped up your lamp, but didn't finish in time for nightfall. Also, buy a set of quality projectors, i.e. Hella, since you're already spending that much time and money into the project.
For more reading, definately swing by the FAQ on lighting here:
http://faq.auto.light.tripod.com/