accidentally installed new apple software 3.0

Someone in my household accidentally installed the new apple software overwriting the atv flash one and now we no longer have access to all the software we were happily using. Before we atempt to reinstall the atv flash, do we have to worry about losing all the data that was placed on the machine - our movies, photos, music etc?

I can’t even access the machine by ftp like used to be able to retrieve the files - any suggestions?