viewing old imessages (for free, on a PC)
I would get PhoneView and connect the device to a Mac (even if you have to borrow one or go to a library) and then save the message database to a more friendly format.

I sadly cannot offer any PC options, but I'm sure someone else here will edit one in to this answer in place of my ignorance or offer their own software recommendation.

Phone View is my go-to tool for this. You could even ship your iPod to a consultant that was willing to do the work for you if you absolutely have no other options.