I am also a newbie to networking, but i would guess the 3 hardwired
computers would have to have a non routable protocol, such as NetBEUI
to connect to each other, but to access the internet they will also
have to TCP/IP installed, this is a routable protocol. File and printer
sharing will be turned on in NetBEUI, but off on TCP/IP

As I said, im also a newbie so i am possibly wrong?