Glo SD card question

I haven't been using an SD card, but my internal disk is beginning to fill up.

When I use a card, do books I buy go there automatically when I'm out of internal disk space, or do I have to do something to enable this?

My disk is a 16 GB Duracell Micro SDHC. Is this compatible with the Glo? And is there somewhere in the Glo an indication that a memory card is present?

Thanks,
Tom