Right now there exist approximately about 10 to 15 different guides on the web supposedly telling you how to upgrade to and jailbreak 1.1.3. The only problem with these guides is that while they for the most part contain much useful information, that information has to be pieced together like a puzzle from all the various guides. So, here you are - the definitive iPhone 1.1.3 firmware upgrade guide.

read it here macrumors