Just joined and thought I'd throw in my two cents. I tried the store kits and they made no improvement. Tried Flix product bought at a trade show, no better. Even my oil change guy said he had an industrial kit he wanted to try on my car for free. A slight improvement but nothing spectacular. My son & I finally decided to try our own idea. Fine grit sandpapers normally used for post-car painting. Used a water bottle to keep the lens wet while we went at it with 800 then 1200 grit. THIS MADE THE BEST IMPROVEMENT!! Overall, it wasn't hazing or condensation or lens oxidation. It was fine dings caused by road debris over 9yrs and 200k miles.
The headlamp housing is a sealed unit and you cannot open it to clean a lens. Light condensation is normal in certain climate conditions. The headlamp housings are vented. Heavy condensation or water intrusion indicates a faulty housing, possible cracked.
The headlight lenses can be cleaned instead of being replaced. I recently cleaned mine using a "kit" made by 3m. I bought it at Advance auto parts and it did a fantastic job. The total cost was about $20.