Correct, you can't. The LED is a completely different setup. You do have options on the bulb you use though as some give off a different tint.
Yup, in a IV you will have Halogens... Nothing to be mad about though, they are projector beams and work quite well from everything I have heard. And no, you cannot just stick LED bulbs in there... And it wouldnt be as easy as changing out the whole headlight assembly either, the LED headlights have an auto leveling system which the Halogens do not.
Well the others have given you the answer. The bonus is that kids can't imitate it cause it's too expensive so you won't have rice rockets with aftermarket LED headlight kits (at the moment anyway).