The restore points are useless. There are a few places to get the firmware:
http://www.felixbruns.de/iPod/firmware/
http://www.iclarified.com/entry/index.php?enid=750
Also, if you just want to restore to the current firmware, just connect your iPhone to your PC, launch iTunes, and click the Restore button. It will automatically download the firmware and restore.
If you get your iPhone jailbroken, use TinyUmbrella or iFaith to get SHSH blobs. Currently they are useless for the iPhone 5, but they MIGHT find a way to downgrade them in the future, and if they do you would need them.