Maybe I have lost my ability to read. Do I upgrade my 3gs with JB'd 3.1.3 to 4.3.1 using iTunes first, then JB with either redsn0w (don't need the unlock) or sn0wbreeze? I have to assume that if I do upgrade via iTunes that the process will leave a .ipsw file on the PC for the JB program to find. Is this correct?