3gs to ios 4.3

[hoorock]

Hi,

Ok so noob is an understatement for me when it comes to jailbreaking/unlocking, etc. I have an unlocked 3gs with Cydia installed running ios 3.13, and baseband 05.12.01. I didn't do it myself - it was given to me this way and I just put my old sim card in it. What I want to do is get it to ios 4.3 so I can take advantage of some new apps that won't currently install. Doing it legitimately through iTunes will kill my unlock right?

What should I use to update the ios? Do I lose the unlock? Is it easy to unlock again? Do I need to jailbreak again?

What is the easiest way to do this? Once again I'm the noob extraordinaire so in the simplest terms would be extremely helpful!

Thanks to any kind soul who reads this!

[M3th0s]

iClarified - Tutorials - iPhone
Have a look at this link. Should give you some idea what the pros and cons are of updating and unlocking your 3gs.
There are a few more tutorials there on how to do that for 4.3.1.
Best of luck.