In reading up on iPhone firmware v3.1.2 seems preferred if one wants to unlock. In shopping for a new (to me) iPhone most seem to have 3.1.3 - the unlock procedure for this does not seem for the fainthearted. So, my question is where I might find a DIY guide for reverting to older firmware (i.e. 3.1.2) - assuming such is possible. Thanks in advance!