When I bought my new DS3 Racing, I knew there were some things I had to do to it, like the engine mounts or the carbon fiber, but the headlights were a surprise when I saw it for the first time. It wasn't a disaster or anything, but it was something I couldn't just let be. The headlights were damaged on the top from the sun in combination with (I think) window washer fluid.

I used this video a lot when doing this. I didn't have jack stands or a lift, so it didn't go as smoothly, but the idea was there.

First, I opened the hood and took out the 4 screws on the top of the bumper. After that undo the clips and unscrew all the bolts holding the bottom of the bumper in place. The middle clips were replaced with bolts on my car (see second photo)

After that, it's time for the mudguards. You don't have to remove them fully, but just loosen the front of them so you can get to the inside of the side of the bumper.

The side of the bumper is next. This is held together with two bolts and it clips onto the fender. The front bolt is easy to remove after loosening the mud guard, but the rear bolt is very hard to reach. I recommend just slightly bending the bumper to the side so you can get your hand and a very small ratchet in there.

After that's also removed, do the same for the other side. You can just lift the bumper off pretty easily after that

Then you can remove the headlight with the 3 bolts! Be careful to also disconnect the cable for it. You have to lift the little flap from the connector that is on the cable up with a flathead screwdriver.

Now just to repeat the process on my new DS3...

Some notes though on the racing version, you also have to remove or loosen the front carbon fiber piece on the bumper to be able to loosen the mudguard.