First off, let me start by writing, that i am sorry. A few good pictures are missing and i do not know what happen to them, so this might not be the _complete_ guide i hoped for, but at least it will get you very far.
Everything you see was performed by a professional aka not me. Removing the front bumper is essential to removing the headlights to install HID/Xenon or LED lights. This is the sole reason this was done.
I don't know the dimensions of the Torx screws, but they should be standard as with many other cars.
The car:
First off, removing screws underneath the car:
Few extra pictures:
Then removing the screws under the bonnet:
After that removing all screws in the wheel arch:
Removing the plastic cover marked as blue will give some access to the bulbs and make it a bit easier to change them.
After removing all the screws in the wheel arch on both sides it should be easy to loosen it and gain access to the screws holding the front bumper.
There are two on each side and my mechanic spend a lot of time getting to the one in the back. There's no space and it requires very small hands. I've marked their approximate location as seen from the outside.
Now the front bumper can be removed. You might need to use a little force.
Only 3 screws hold the headlight in place:
Remember to disconnect the wires to the headlight.