If that is the only problem the skis should be fine. It would be good to have them do the tightening, so if there are any spinners no one can blame it on you.
Without looking at it, I'd say the proper fix would be to pull it, check to make sure the mounting holes aren't too proud, and relube with glue and rescrew until I'm satisfied. If I looked at it, I might be happy just running the screws down tight. Chance of one or more spinners is pretty good, so I say let them take the risk...besides they should be forced to fix their bad work as a matter of principle.
The skis will be fine, and like jaobrien6 said REI typically has excellent customer service (though not necessarily as competent or knowledgeable as a specialty retailer) so I wouldn't sweat it too much.