Hi maugin! I'm a newb geocacher, but a long time happy Mac user (over 15 years, no viruses). I suggest you look at this site:
http://chimbisimo.googlepages.com/
chimbisimo outlines how to use GPSBabel+ to talk to a Magellan. I have an eXplorist 210 and it only took me about half an hour to download GPSBabel+, figure it out, and get data onto my GPSr.
Go for the Mac!