Upgrading to 4.1/4.2

[vadi20]

I am new to iphone stuff. I have a iphone 3GS with 4.0.2, fw 5.13.04, jailbroken (with limer1a) and carrier unlocked. I want to upgrade it to 4.1 or 4.2.
Let me know how to upgrade it?

[Simon]

If you have windows you can follow this guide: HOW TO: Jailbreak iOS 4.1 with Sn0wbreeze 2.1

If Mac follow this one: iClarified - iPhone - How to Jailbreak Your iPhone 3GS Using PwnageTool (Mac) [4.1]

You have to restore to a custom firmware in order to preserve your baseband so that you can still unlock after.