Yes, it is POSSIBLE to swap just the lens, but IMO NOT worth the time, money, and effort. It takes a heat gun/oven to separate the 2, then you have to go through all the work to carefully pull them apart without damaging them. If you decide to try this route, you'll find detailed instructions on how to do it by just using Google and search for something like "Black Housing mod", or "Projector Mod", or even just "Headlight Mod" and it doesn't really even have to be car specific. There's a ton of videos on Youtube documenting how to do it on most cars. It is much easier to find a headlight complete on eBay, or even a pair though. A couple hundred bucks should pull you in a non-HID set for an '04. Typically, for the STi set with HIDs you'll pay more around a grand, just to keep you informed. PM me if you have any questions, as I've taken apart tail lights, headlights, blinkers, you name it on almost every vehicle I've owned. Just trying to find the initiative to do it on my '08 and rip out the ugly orange reflectors. I personally always use a heat gun, but everyone has an oven, so that's the most common way to do it if you want to only swap the lens. The lens is almost always the part to go defective, so that's why you'll rarely find it separate. As always, that's just my $.02