My left xenon turned red and died

How to replace the xenon dipped beam on Octavia 2.

Is there any guide?

There is no official guide as they very rarely blow. The replacement bulb size for the factory fit xenons is D1S and you are looking at around £80 each in the UK. I would see how much your local dealer would charge for a replacement, although the bulb would have to be ordered. Depending on how old the car is you may be able to argue that they are suppsed to last the life of the car and should not die on you and get it replaced for free, but they would more than likely refuse.

Yes they refuse to replace the lamp.

The car is 2,5 year old and 3000 km.

Looking at some notes I have, I believe it is quite easy to replace the Xenon bulb yourself.

All you need to do is remove the headlamp from the car, unscrew the back cover off, disconnect the transformer from the bulb then take off the screws holding the bulb in place and remove the bulb.

Just make sure the bulbs are D1S and 35W

Try your local car spare shop a friend with a Renault did this and got two for the price if what a dealer would charge for one