Actually I think you will find the new ipod nano (quite possibly the others as well) don't actually come with any software these days. I think there is a statement on the box that says you need an internet connection to download itunes.
roughly how much space would a audio CD take up in MP3 format?
This is a bit of a variable because it depends on the bitrate that was used when converting, on average you can say 1mb per minute, 4 min track 4mb.
To put a audio CD on to a iPOD or similar, is it a easy task to convert it to a MP3 file then send it to a iPOD?
Yes it is fairly straightforward.
To add music from your own CDs, insert an audio CD into your computer and then drag the CD icon that appears in the Source list onto the Library icon to add the entire album, or select the CD icon in the Source list and then drag whatever songs you want from the right-side pane to the library.