iPod Nano 4th Generation Teardown
I found another website that explains the process of taking the Nano 4th gen apart much better than here. Perhaps ifixit can refer to it and make it more clearer to other people how to take them apart much easier than described above.
Sorry ifixit, but your description wasn't as clear here and i ended up breaking the click wheel cable. don't want others like me to do the same thing here cos your website does have great guides, just this one wasn't as great.