To add to this post, I just recently switched from using PCs all my life to Mac's, and I'm thoroughly enjoying it.
There are two ways to move your music from 1 computer to the other:
1) If your ipod is set to update manually, you can get the program Senuti (which is great, needless to say) and copy the music files from your iPod onto your new Apple. Then you can add the files to the library, consolidate the files, and delete the originals and itunes will be set.
In this case, if the ipod is set to update automatically, it might erase the files so be careful doing this.
2) Or like pat++ said, you can use an ethernet cord and open a network connection to your PC if you share the music folder.
Good luck with the decision, either way getting a new computer is always fun.