Q&A

 Master

For $20 to $30 Meguiars has a headlight restoration kit http://video.google.com/videosearch?q=meguiars+headlight+...# call your local auto parts store or buy it online

 Master

Unless your Audi A6 Quattro is an exception to the rule the lens is not replaceable, you must replace the complete headlight assembly. You may wish to check with your local Audi dealer to confirm this. You may use the following link to find your local dealer - http://repairpal.com/audi-dealers.

 Journeyman

the lens has clips and is glued to the housing. i personally have replaced the lenses on my 2001 a6 (same as yours). i used my regular lenses to put on a pair of xenons a customer had replaced for your issue. the thing is the lenses are not available seperately. there are companies that sell waxes and even gel coating kits to fix dull lenses but if you want the best result, buy a set of xenon headlights (complete) and install them. no wiring needed, plug and play. try 1800vwparts they may have some.