I don't recall there being a problem seeing the files in a file manager even when I was using iTunes, but I may be wrong. The problem was that when transferring with iTunes the files were given crazy names and put in folders F01-F99 or something.
Now I remember: There are some hidden folders when you view the iPod in explorer. Make explorer display hidden files/folders and there should be a folder called iPod_control (IIRC) and within it a folder named Music and voila: The crazy F01-99 folders
The files are in those. As I said, the files too have been given strange names, so what you need is a mp3tagger of some sort (I recommend the free Mp3tag (google it... sorry.) that can rename files from tags, cause the tags are still OK in the files.
Hope that helps, and sorry about any bad spelling or explanation, I'm a bit tired and my daughter is crying... GTG