I use this website to download all of my music...
http://www.youtube-mp3.org/
All you do is go to youtube and find the song you want, copy the URL, paste it into the website and press convert, then download. Once you do that you can open it into your iTunes and put it on the iPod.
Best of all, its free!!
good luck, if you cant figure that out, I can help you with any other questions.