we know that when ever new iOS come in the market, you just want to use the features and try it.
well but its scary if you use software unlock for using you phone...
the best method is to wait for unlock and jailbreak but if you really wanna try it
preserve your baseband and update with the custom ipsw.
how to do it?
1- Download Redsn0w's latest version available
2- go to extras or option other than jailbreak
3- choose create ipsw or custom ipsw.
4- create the ipsw and use that created ipsw with iTunes to restore normally