Hi Kevin,
Welcome aboard.

I can't help as i never heard of them before.
Anyway, i would be cautious with such of sites. Seem to be a good product but there is at least a leack of support, no online chat and their FAQ is extremly poor. (More a kind of testimonials than a real FAQ...)
Indeed, i know the princip of CMS (Content Management System) and i don't see why you won't be able to set it up with your Yahoo Store BUT as i never heard of this service before i would take the time to send them a mail where i would ask all my interrogations in.
Just my 2 cents.
Anyway, good luck with your future project.
Let us know how it goes.