1st: Yellow clould mean a few things, please check the status of it on the manual for solid vs blink
2nd: Don’t go back to that shop, just the fact they told you the drive is encrypted, is enough, at least it would be for me. I would also doubt the board is bad.
And you are on the right track. These devices are Linux OS. So just mounting the drive on a Windows or Mac will not show the partitions/files. You need to install some software for it (see guide below). Hopefully they did not mess it up trying to mount/connect to the drive.
my .02 cents, your unit did not upgrade completely to a new firmware. You will have to unbrick it. Here is a guide, there are two versions, both mention on the guides.
http://community.wd.com/t5/My-Book-Live/GUIDE-How-to-unbrick-a-totally-dead-MBL/td-p/435724
And last, my favorite shared link! Backup, backup, backup
http://www.cnet.com/how-to/digital-storage-basics-part-3-backup-vs-redundancy/
