this may be old news, but garmin has some neat software that will automatically check ur software rev in ur garmin gps, and update it if necessary.
i don't know what all models it includes, but it updated my foretrex 401 right quick, and i'm sure it will work on an etrex series gps.
http://www8.garmin.com/products/webupdater/ (http://www8.garmin.com/products/webupdater/)
bill