How long does it take to import a library using home sharing?

I have about 82GB of music on an older iMac and want to import it permanently into the iTunes on a newer iMac but have never done this before.

Before I start, I'd like to know if I'm going to be tying up my computers for a week!

Should I go for the whole 4,000-plus songs at once, or should I try to plod through playlist by playlist and tell it each time not to import songs that may already be in the new computer. (If I do that, will the song show up in the playlists anyway?)

How have other users approached this with large libraries and what has their experience been like? I'm so glad there's a community here to share their experiences and help other Apple owners!

Thanks so much for any and all responses!