So I just bought an iPod Touch, OTB 3.1.3, but my iTunes shows the new version available is 4.0.2, if I upgrade to this can Spirit or Jailbreakme, jailbreak my iPod? If not, where can I find the 4.0.1 firmware?

Answer to your questions is NO and google is your friend LMAO!

Read http://blog.iphone-dev.org/post/1013332740/winning-moves for the details on why the next jailbreak will be for 4.1 (if at all)

Apple has been 100% predictable with when they release new hardware and major iOS releases - that allows the jailbreakers to release a new jailbreak when they will make the most impact.

You did not do your research and buy an iDevice at the right time when jailbreak and unlock were likely to be available.

Jailbreak is not a privilege. Don't feel that you are entitled to a jailbreak for each and every minor iOS release.