1. Get the Griffin iMic for $35 (unless you have rca connectors/sound card on your current mac).
2. Go to version tracker and download Audacity. Good freeware recording program with basic editing features.
3. Then you can play your tapes to your computer, record, and then export aiff files (or wav).
4. Download the Blade encoder (version tracker or google it) and create your mp3 files to burn to cd.