The good news is that its a very straight forward process to revert your iDevice back to its unjailbroken state whilst maintaining the data on your device. You will of course loose any apps you installed with Cydia and any data associated with those apps. Instructions after the break...
Steps to Unjailbreak:
- Plug your iDevice into your PC or Mac
- Open iTunes and select your device from the left hand menu
- Click the restore button in the right hand window pane.
- You will be prompted to back up your device so go ahead and do this.
- Now iTunes will back up your device and restore iOS to its clean state.
- When the restore is complete and your device reboots iTunes will ask if wish to restore from the back up you just made.
- And relax. You are back to a clean unjailbroken device with all your data still intact.