Cannot Sync iTunes Library Folder when it's on External hard drive

I store all my music on my external hard drive, and have set my iTunes music folder to be a folder on my external hard drive. Now, when I tried to important my iTunes library, Songbird immediately assumed that the file path would be on my main hard drive, with the default iTunes music folder. This, of course, makes it impossible for me to play my songs via songbird (though it works perfectly well with iTunes)

Now..the inherent problem is that I cannot see of any way of changing the file path, or default folder or whatever, of the song through songbird. I'm not sure if there is a way to and I'm just missing it, or if that hasn't been implemented. More importantly, I definitely can't find a way too do it en masse, which is important since my iTunes library contains 20,000+ songs, and I certainly don't want to do that one at a time.

Help!