I just got my refurb 60Gb Video two days ago. Pristine condition by the way. It is what I think you are referring to as an original 5G. Its's version number is 1.0.2 (or something like that. When you connect to iTunes, it will tell you that there is an update to 1.2 that you can get. That doesn't give you ALL the functions of the G5.5 or "enhanced" iPods videos, but it apparently give you gapless playback and some other features like ability to add some games.
I have been having some problems updating to version 1.2 and I have seen others having the same issue. Just got off the phone with tech support and they told me something to try. I'll be doing that tonight.