MP3 players: How do I consolidate 4 iTunes libraries/2 iPods to 1/1?

How do I consolidate 4 iTunes libraries/2 iPods to 1/1?

We have 4 PC’s, all running XP, each with its own unique iTunes library. They’re not linked by a network, living in 2 different homes.
2 PC’s are synched to their own 30 GB 2nd Gen iPod, both Pods maxed-out.
2 PC’s have no iPod synched to them.
Then, we have a blank 80 GB iPod 2nd Gen.
I want to move all 4 libraries onto one PC, throw out the duplicates, and then load it all onto the 80 GB iPod leaving one computer with the entire library.
I’m fairly adept with iTunes, but this seems like an overwhelming task.
There must be some logical way to accomplish this without losing my mind….
So, where do I start?
Thanks for any input!
Sazam