3gs 3.1.2 -> 4.1? Help

[gausher]

Hi I currently have a 3.1.2 firmware with 4.26.08 baseband on my 3GS.
been reading and getting confused with all these jailbreak/unlock options.

Which is the best option for me to upgrade in windows to a 4.1 firmware? Im with tmobile & need to unlock it too.
thanks for the help!!

[iYeow]

If you have 4.1 shsh blob, you can check that out from the front page of cydia. Then to preserve your baseband, you need to restore to a custom firmware of 4.1. You can use snowbreeze 2.1 to build a cfw of 4.1. Run tiny umbrella, plug iphone in, click save shsh, start tss server,Use redsn0w to put you into dfu mode ,
Run itunes and shift + restore to cfw of 4.1