Help Please

[copper]

I am still on 3.0 on my Iphone 3g. Stupid I know but anyway, is it possible that i can go to 3.1.2 and jailbreak my iphone still right now. I keep seeing downloads for restore 3.1.2 around but dont know if this is it or not. Just trying to gets some apps from the app store but some have to have at least 3.1 upgrade to buy them. Any help would be great. I have a mac.