Well, I think it all depends on what your goals are. For lowest inital cost, your solution would win. Ongoing cost is a subject of some debate. The numbers I have seen indicate that currently *nix has higher ongoing support costs because knowledgeable people cost more than windows people.
As for how to do it, the best place to start would be
www.samba.org they have lots of good info there. It's a pretty basic config since it doesn't sound like there is going to be a Windows domain involved.