As long as the ding is small then they will swap it. They will attempt to run a test on the phone first to see what is wrong so if you have any ROM that is not sprint I would suggest to make it factory again and I think you will be fine. The store is really great about swapping out messed up equipment and if it is deemed that you caused it if you have the insurance you can pay a 100 dollar deductable and they will send you another one right out.
I would take the phone in and tell them what the problems you are having are and they will more than likely just start working on the phone and offer to replace it if it is not working correctly.
Good luck and dont be nervous because you have options within Sprint to get it either fixed, replaced, or advanced exchanged.
