Im not sure i understand what you mean, but i think you shouldn't be worried. The only way to lose your stuff as you mentioned, is to *restore* your device using iTunes. If you just want to sync your songs (or whatever else) to your iPod, feel free to do it, it doesn't matter if your device is jailbroken. It will sync whatever is present on iTunes and not on the iPod (or vice versa) or you can manually choose what to sync in it. So to sum it up, feel free to hit the "Sync" button, you won't lose anything from your device 🙂