Yes a router will work fine, and contrary to popular belief you dont have to use the Airport. Any router will work. My macs are wireless so i use a linksys wireless router.
As for file sharing does he use os-x, if so then it has somba built in. Go to preferences, sharing, and turn on "windows file sharing". No need to use Dave with OS-X, just delete the program. If OS-9, then stick with Dave.