I am in the excact same situation as you are (and stuck at the same point). I would love to get this working so that I dont have to worry about updating the exchange rate maunally every day. Did you get this working yet?
## EDIT ##
I found this walkthrough and so far things look good.
It's for a previous version of Prestashop, but I think it's still good. I have made a note of the current values in the currency section and will know in 24 hours if they have auto updated via the new cron job. Hope it helps