Download ExpertGPS
http://www.expertgps.com/
if you buy it it's around 75$, you can then copy all the data from your GPS SD card to that as a backup and view it on your home computer overlayed on maps.
if you download the free version you can then upload the file back to another SD card for use on a new GPS
I'm not personally familiar with the type of card that garmin used on your model... did they use a regular SD card or something else?
If it's not a regular sd card, see if you can get your hands on a card reader for that model.
Hope this helps.