Help with Updating iPhone 3GS from 3.1 to iOS 4

[3magin8]

Hello,

I couldn't find any straight forward answers on updating.
It's been awhile since I've updated my iPhone.

I have an iPhone 3GS on 3.1 with bb 05.11.07
The phone was jailbroken with blackra1n and relies on ultrasn0w for unlock (with t-mobile).

I would like to update my iPhone to the latest version. I still need jailbreak and the unlock.
What's the best way to go about this? And please explain the steps I need to take.

[iYeow]

Restoring to custom firmware 4.3.3 if you have 4.3.3 blob for verification of your restore.

[3magin8]

I use windows 7. I've never restored using a custom firmware. Can you please elaborate or suggest an alternative.

[iYeow]

Use tiny umbrella to download all your blobs.
Download snowbreeze 2.7.3 and build your cfw of 4.3.3
Start your TSS server
Put iPhone into pwned dfu mode
Run iTunes and restore to cfw of 4.3.3
Install Ultrasnow to unlock.