Whenever you are restoring or resurfacing a light you MUST put a new protective coating on the lens - otherwise you are just polishing raw plastic which will oxidize (haze) or scratch again quickly. I had my lights done by a local mobile-shop called ClearVu - Eric the guy who runs it uses top quality chemicals that cost $30-$40 themselves, and charges between $50-$80 depending on the size of the lights etc. It's a quick 30 minute job and turns out awesome.
Checkout my before and afters on my 03 Altima:
BEFORE:

^Needless to say I couldn't see much at night LOL!
AFTER:
Obviously, this thread was started a long time ago and has been bumped, but it still remains true today that no matter how you go about restoring your lights make sure you use a protective sealant/coating designed for lights and NOT just a plastic polish or you WILL be doing the job again in just a few months time!