When I tried to install Linux on my iPod. I, like many others, screwed up my nano. Then I searched all over forums looking for a possible fix. I couldn't restore the Apple firmware because it couldnt mount the ipod. I pretty much figured I was screwed, unless i knew linux. The tutorial for the linux fix didn't seem too user friendly either.
http://dvd-ripper-copy.blogspot.com/2006/10/how-to-fix-your-nano-when-you-failed.html