99% of the time the damage is on the outside. it's very rare for seals to fail or get enough condensation (from the atmospheric vent) to become unsightly. i talked to a guy in a parking lot one day and he was told by the dealer to swap out the entire lens on his mazda (don't know how this would be cost/time effective if you're having to buy a pair of headlights for just the lens). i showed him all the damage was on the outside and it could be removed in just a few hours.

 

how much are the lens by itself ? And were can i get them ?

 

Once the yellowing gets too advanced, it will be necessary to use an aggressive treatment on the lense which usually requires light sanding. If you are not familiar with the process, I would leave it to a professional. The aftermarket treatments such as Meguiars Plastx does work, but it depends on how bad the oxidation gets. Many owners don't realize that if you continually treat the lense with just polishing wax every few months the lenses will never get yellowed. I've done this on my 04 G35 and the lenses still look brand new after 8 years of ownership.

 

+1 on restoration kit

 

I had to buy a new lens for one of my headlights cause i left it in the oven on the wrong temperature and melted the mother F***er. i got a new one from the marketplace for like 85 shipped.

 

I just opened up my headlights to black out the side walls. and used some water mark remover and a high speed buffer at speed 30 my **** looks Brand new 110% dont use any of that BS restore kits. especally any sand paper if not done correctly will mess up ur lights