You want to remove the whole clear plastic cover? WHY?
Unless water or smoke got in there, I'd STAY THE F*&% OUT of there.
My understanding is that the inside is coated and once you touch it, it's a PITA to completely clean.
In order to get it off, you have to pull off your bumper and remove your headlight, then use a heat gun or the oven to melt the silicone adhesive and then do it all in reverse to get it back together.
Go the the Mod database, then look for the Halo...
Here:
http://forums.g35club.org/zerothread?id=340467
The write up is for something completely different, but it gets the headlights off and the lenses off too.
I think search engines were made for only a small subsection of the population. Which means the programmers FAIL.