Restore 1st gen iPhone

[cmefly]

I want my jailbrocken 1 gen phone to get the latest update.
It works fine, and is only jailbrocken, not unlocked. It has Cydia on it. Don't really want it anymore.
Using ATT and has version 2.1 on it. I use a MacBook Pro with version 10.5.8

Would be a restore to factory setting via iTunes be enough?
Will it still work after re-sync my stuff??

Thanks very much for any help !

[Moi un Mouton]

Just plug it into iTunes, do a back up, do an update (or a restore if you prefer), then restore from back up (if you want)