How to update my unlocked iPhone 3GS to IOS 5?

How do I update my iPhone to IOS 5 and preserve my unlock?

iPhone: 3GS
IOS: 4.1
Baseband: 05.13.04

I know you don't have AT&T but call them, they are the only carrier that supports the 3GS in the USA.

Here's how I updated my iPhone 4 to IOS 5.
First, download the latest version of iTunes at Apple's website.
Then, Open iTunes.
Plug in your iPhone to your computer.
Go to your iPhone's "section" where it tells you how much GB you have left.
Then there should be a button that says "Update" Click it.
Then when it's updated, it should have the original apps, Safari, App Store, Music, etc.
Then sync the iPhone to your computer. It will install all the songs, photos, and apps that you originally had.

There you go! If it doesn't work, go to the Apple Store. I'm sure they will help you.

If you update it will be locked.