i have done the full red conversion for my iphone 4, cracked the front screen and the full conversion kit was cheaper than paying apple £139 to sort it out themselves. I don't have a warranty anymore but I'm not fussed as that never covered cosmetic damage in the first place.
Looks amazing paired up with a bumper case, I'd suggest it to anyone. PM me if you want more details if you're in the UK as the guy who did mine can do nearly any colour. dark blue, red, white, yellow, gold, transparent, pink, green... they all look pretty amazing.