dont worry about an aircard.
just jailbreak your iPod and install OpenSSH on it, then get a program called iPhone tunnel Suite (2.7 is a good release though it's kinda hard to find). Just do a google search for iPhone Tunnel Suite 2.7 and that is a stable release. Set it up according to your iPod specs, restart your computer, and see if it works.
Do a google search on how to use iPhone Tunnel Suite, and you can find a good tutorial. You need firefox to get internet, unless you can set up a SOCKS 5 proxy through a mac computer, and then you are good to go. Trust me though, you need a tutorial.