Upgrading to 4.2.1 from 4.0, iphone noob

[forumss]

I have 4.0 installed and jailbroken and unlocked (carrier locked, unlocked it with some h4x).

i wish to upgrade to 4.2.1 but i cant comprehend exactly what needs to be done, for example people talk about upgrading modem firmware etc. I just dont want to upgrade something accidentally and unable to unlock it again.

info:
installed currently ios 4.0
iphone 3g, 8gigs
modem firmware 05.13.04
model MB489X

[iYeow]

To preserve your baseband and to be able to get to 4.2.1, you need to restore to custom firmware created by Pwnage tools 4.1.3. Use redsn0w 0.9.6b6 and browse to stock 4.1 , check only the box DFU mode only to put you into DFU mode or you can use Pwnage tools to put you into DFU mode and then run itunes > shift/Alt/Option + restore to this Custom fw of 4.1.2. Unlock again with Ultrasn0w from Cydia.

[forumss]

To preserve your baseband and to be able to get to 4.2.1, you need to restore to custom firmware created by Pwnage tools 4.1.3. Use redsn0w 0.9.6b6 and browse to stock 4.1 , check only the box DFU mode only to put you into DFU mode or you can use Pwnage tools to put you into DFU mode and then run itunes > shift/Alt/Option + restore to this Custom fw of 4.1.2. Unlock again with Ultrasn0w from Cydia.

this sounds a bit confusing, you have firmware 4.1.2 and 4.2.1 and 4.1....

[iYeow]

Sorry, firmware 4.2.1, there is no fw 4.1.2... So it is just firmware 4.1 and fw 4.2.1. Typed too fast & ended typo error..Lol