IPod jailbreak/firmware question?

[Joe]

I have a iPod 3g with 3.1 firmware I want to update to 4.1 because everytime I try to jailbreak it with jailbreakme.com it crashes. So I tried updating it on iTunes but it only has 4.2 firmware download which I don't want but even if I try to download it it says I need to update my iTunes which my computer is not letting me do. Is there a way to choose which firmware you want? I tried doing direct downloads but it says safari can not download or somthing like that. And is there another direct jailbraking website that could work on 3.1 firmware? Any help is greaty apprechiated. Thank you