Help Please about iPhone 3g
 

Dear All

Kindly I got used i Phone 3g and it's data is the following:
Version: 3.0 (7A341)
Carrier : Vodafone 4.0

Model : MB496AB

My request that I need a guide to how I can update the software of this iPhone as the one I got it from told me "care not to update or it will close"
Also about the message about update for the carrier settings on the iTunes.

So please try to help me and excuse me I am not good on iPhone so please try easier explanation.

Thanks in advance.