How to update and jailbreak to IOS 5 from 4 on Iphone 4?

If I'm on 4.3 jailbreaked and unlocked with gevey on tmobile and, and I want to update to IOS 5. What are the steps? If I update to IOS 5, will I lose my unlock on tmobile? I don't mind if I can't update my jailbreak. As long as I can use my phone on tmobile, then it is ok.

Added (1). Because the apps now in the app store needs IOS 5. I can't get it.

The gevey sim will not work on ios 5