I will answer ALL your jailbreak questions.

[x999x]

1) Restore your device to factory settings

2) If you have an appointment with an Apple Genius to review your issue, there is a good chance they will take your phone in the back and basically swap it out with a refurbished model. This has happened to me on a few occasions. They'll typically sync all your data back for you while they're in the back, however this is entirely dependent upon them having phones readily available, which is why I schedule an appointment and let them know ahead of time that I am having a hardware issue that likely needs replacement.