Listen if you're worried about getting your phone scratched then be extra cautious. If something happens then go to an Apple Store and simply say that the iPhone's battery life has never been good and that the signal is not as good as your wife/friend's iPhone 5. Say that you believe your iPhone is defective and that you want a replacement.
Apple will take it in, test it then replace the exterior (which is cheap for them) then use it as a refurbished replacement for other customers.
Apple will take it in, test it then replace the exterior (which is cheap for them) then use it as a refurbished replacement for other customers.