Merge 3 iTunes Libraries

I need to combine the iTunes libraries from a PowerBook G4, MacBook Pro, and one that's on a firewire hard drive. All 3 iTunes libraries need to be combined into one new library I created on a Lacie HDD. What is the best way to do this while retaining playlists and all the metadata?

In the end what I need to accomplish is this:

G4 iTunes library (default) is empty
MacBook Pro iTunes library (default) is empty
External HDD iTunes library is deleted
All libraries are merged into one that is held on the Lacie HDD
Duplicate songs, playlists, etc. are identified and/or erased.

This way the Lacie drive can be connected to the G4 (for example) and the library on the drive can be selected to listen to. OR the default library can be loaded and select songs or playlists can be sync'd to it keeping the hard drive relatively empty.

What is the best way to do this?

I started by connecting a brand new Lacie hard drive to the G4. I created a new iTunes library on this hard drive. Then I copied the contents of the music folder on the G4 to the music folder on the hard drive. I then opened iTunes on the G4 and exported the library. Once that was done I opened the iTunes library on the Lacie hard drive (holding the Option button while opening iTunes and choosing the library that is on the Lacie HDD) and imported the file that the G4's library made.

Here's the thing. The library from the G4 has over 6000 songs in it. iTunes has been copying these songs for 2 hours. Why is it copying them if I already put a copy of them on the Lacie HDD? Seems to me that it is rebuilding the library rather than picking up where I left off (just on a new drive).

Is there a faster way to do this?

Do I need to load the library that's on the other external HDD into iTunes on one of the computers so I can then export it?