I have an iPhone 3G that didn't update since 3.0 and my Modem Firmware is 04.26.08.

so far all the tutorials that I see are outdated, confusing or for iPhone 3GS or iPhone 4.0.

can I upgrade my phone to latest OS (assuming it is 4.3.1, if not let me know) without upgrading the modem firmware?

If I have to upgrade the firmware, which version and how should I do that?