Setting up a workgroup with leopard server

Okay so here is the layout, I have a PowerMac G5 running leopard server with pretty much all default configurations. I have a business line to my house with one static IP and a cisco small business router and switch. I also have a domain name from godaddy. I would like to host file sharing and email mainly with the server and possibly vpn access. So I guess my question is with everything I have what would be the idea setup. I am very computer literate but network administration has never been my strong suit. Right now there will maybe be 4 or 5 people with any kind of access to this network with no real plans for expansion. Any suggestion would be appreciated.