Q: i need to get back cover off my ipod classic.

hello i have a ipod classic 120 gb  ,god i love it . well the other day i droped it and it started actkting  funny it would turn on and show music but would not play. this morning it would not go to music it showed a red x on screen . i tried to run it through test and it gets stuck,on{ cant open devicel }  error!  diag halt . what do i need to do ? some one said it may be the hard drive cord or some thing like that ,   help please.