I saw a ton of posts talking about downgrading from 4.0.2 to 4.0.1, but I currently have a JB 3gs with 3.1.3 and would like to upgrade the software to 4.0.1 so I can JB and sell on ebay. Does anyone have a step by step tutorial on how to upgrade to 4.0.1. My itunes only gives me the option to upgrade to 4.0.2.