Depends what type of song files they are. If they are mp3 then no need to convert. iPod can import mp3, m4a (mp4 audio), apple lossless, wav & aif. iPod cannot import mp3pro, wma, real or ogg vorbis. If your iTunes can import the songs then all you need to do is connect your iPod. How to transfer music to my iPod (& iTunes) {click on link}

Personally I preferred manual updating my iPod, however some people prefer synching the two ... adding playlists to iPod.