Forgive me if you know these things already...they are very basic.

First off, make sure your Ipod/itunes library is storing songs in MP3. You have to set this up in Itunes as the default otherwise it stores / rips files in apple format.

Itunes stores the music files in directories, usually by artist / then CD. You find the MP3 files at the bottom of the directory tree. Depending how your MP3 player connects to your computer, you may be able to drag and drop onto it. I do this with my daughter's cell phones. They appear to be a USB drive to the computer.

As far as a more full featured library app, I don't have any info. I think the generic MP3 world is all looking for an itunes equivalent.