Need help to upgrade from 3.1.3 to 4.1

[lejardin]

I have an unlocked and jaibraked iphone 3gs 16gb version 3.1.3(7E18),Model #MB716LL with baseband 05.13.04
It's possible to upgrade to 4.1 version?Thanks a lot

[Simon]

Do you have 4.1 SHSH?

[lejardin]

I don't think i ahve,how do i know if i have it and where to download.Thanks again

[Simon]

Download tiny umbrella, connect your device and press save SHSH.

[lejardin]

Yes i have the SHSH saved on Tiniumbrella,i have both 4.0 and 4.1
What i do next.Thanks again

[i.Annie]

Create a custom firmware for 4.1 with sn0wbreeze 2.1. Then use redsn0w 0.9.6rc8 to set device into pwnes dfu mode. Then open tinyumbrella and start the TSS server. Then open iTunes and shift+restore to custom 4.1. Be sure not to accidentally select stock 4.1 or you'll lose your unlock.

Then when it's done go to Cydia to install ultrasn0w to unlock.