I have to take my phone back to the Apple Store because the vibrate function stopped working all of a sudden. Can someone please tell me what I need to do to the phone BEFORE taking it in since it's unlocked? I'm using my t-mobile service with the phone and I unlocked using the unlock method for OSX on this forum. I don't know how far to restore it nor how to just so that they can not see that the phone has been unlocked and that the vibrate function and switch does not work. I just need help. I bought the phone brand new and have only had it for 2 weeks

Can someone help me out? I am a novice at all of this.
Thank you in advance.