The best way that I found out to EJECT A GARMIN GPS and to update the maps is to:
1) In the "FINDER", (after opening a "NEW FINDER WINDOW" under the "FILE" pull down TAB", OPEN / double-click the "APPLICATIONS" folder on the far left side of the finder window.
2) In the APPLICATIONS FOLDER open / double-click on the "UTILITIES" folder.
3) In the UTILITIES FOLDER - open / double-click on the "DISK UTILITIES" program.
4) Your Garmin GPS will now show up on the left side of the DISK UTILITIES listing of hard drives and other devices connected to your computer.
5) Click on your Garmin GPS model listed on the left side of the DISK UTILITIES program, which will be high-lighted in gray after clicking on it once.
6) On the upper top left of your screen, click on the Disk Utility "FILE" TAB, use the pull down menu and click on the "EJECT".
7) After EJECTING you GPS follow the Garmin instructions and "UNPLUG YOUR GARMIN" from your Mac for at least 5-10 seconds.
8) POWER OFF your Garmin completely.
9) Make sure you now QUIT the DISK UTILITIES program as sometimes it won't let the Garmin downloading of the software to begin if the Garmin was just previously ejected.
10) Plug the Garmin back into the Mac and be ready to wait for up to a minute or so before the software starts to download into the Garmin (the download time will vary from 20 minutes to 3 hours depending on your web connection download speeds),
11) MAKE SURE NOT TO DISCONNECT OR BUMP THE GARMIN OR ITS CORD INTO YOUR MAC DURING THE SOFTWARE DOWNLOAD PROCESS!!!
Hope this helps you guys. It worked for me.