Returning an iPod that has been opened?

Hi, i've received an ipod touch generation 5 for christmas, but i really just want the classic so i can store more music - not really bothered with apps etc, i spend enough time on the internet as it is! The only thing is, my sister opened it and charged the ipod for me, although it was never used. Will Apple allow me to return this ipod or exchange it? I've heard you cant bring it back once its opened :/