well, i was reading the manual and it just vaguely states under things that void the warranty. "5. Modifying the Xbox"
I don't think they'd care. I mean they let you put skins on, whats the difference. I think ill email gameconsoleskins.com ask em if it voids the warranty. If so, I can always swap back the the green jewel to ship it if it breaks.
I did find something interesting on the web (lost the link), this guy modded his xbox, sent it back, and they fixed it because he just broke off the top, didnt unscrew it. lol.