Hi guys, I know its a few years to late but I thought ide add my story as it may help someone down the line.
Ive got an 2002 S3 8L and strangely when I bought it, one headlamp looked brand new, and the other had the cloudy/rough deterioration to it.
So today I decided to clear it up, and I followed this link:
3 Ways to Repair Oxidized Cloudy Headlights with a Headlight Cleaner
Now to get to what this thread is really about, I decided to clean the inside as well, and so I removed with great difficulty, the front plastic protector lens/case.
It is glues on using a sort of foam sealant which was a pain in the neck, but i finally managed to get it off. Now what i wasnt told is how delicate the chrome finish is on the inside of the lamp unit and on that little bit of plastic trim that comes off inside the lamp.
So as you could imagine, I went to scrub it with a damp cloth and window cleaner, and the ****** chrome came straight off in my hand. Luckely I had started on the plastic trim piece that unscrews from the lesne, and not the headlight unit itself, as a new xenon lamp looks like over £300.
Ive followd all the steps in the link I provided, which was wet n dry paper, polish, and a extremely good buff up with a electric buffer, and it made it much butter (i couldnt see all the diagonal lines on the lamp before and now they are there as clear as day) but its still not good enough as the drivers side one looks like new.
I went to halford to get some chrome spray paint to redo the plastic trim piece and oh my gosh, how bad it was. Complete miss representation on the can, as it looked chrome, the guy i asked about it (who claimed he used to paint metal gates for a living) and well it came out matt (said gloss) and I know how to spray paint.
So I am going to buy a new lens for me light and if anyone is interested in a second hand passenger side lens, let me know...
Conclusion: it can be done and you can take the lamp to bits, its tricky, requires lots of levers and patience and you have to break the seal.