Currently my iPhone 3Gs is on iOS 5.01. I'd like to use it on the T-Mobile network. What are the steps required to make it happen? I think it's obvious that I need to jailbreak the phone. However, googling around around it is unclear whether there is a reliable (untethered) jailbreak for 5.0x. Do I need to downgrade the OS? If so, to what version and how? Any additional steps I need to take?