Sprint is $100 deductable $7 a month. Sprint's policy is if they can't fix it you get a new one. If they don't have your phone in stock you get an equivalent phone (which can be better) or the next best thing. If its from a phone defect you don't have to pay the deductable.
I used a crappier case than the one that you have. I dropped this thing pretty hard onto hardwood and the pavement. Never cracked. Had a scratch on my screen but I had a screen protector so it was alright. You might have dropped it on like a small rock screen first to cause that. Unless you had a "juggling" event and hurled it to the floor. lol