I have installed the version for 1.3.8 and think I have set up the daily cron job to automatically keep it updated, will the feed just update the products that are not already there or overwrite the existing ones, needing to wait another 24 hours for them to show up (by which time it would have updated again), so in theory never showing the products?

Sorry if it sounds like a stupid question but I really don't mind admitting that I know nothing about it, so if anyone could shed some light ;)