dont really understand what you're trying to do. You just want to substitute your "main" pc with your new linux box and have it do exactly the same job?
i've never done usb networking so i can't help you with that element. as for everything else, i can't see any reason why the networking aspect shouldn't work out of the box so long as you're using dhcp.
if you want to give other users access to the files on the linux box you will have to use samba. Apache should already be listening on all interfaces if i recall correctly. if not, you need to add
to your httpd.conf file to listen on all interfaces. alternatively, replace the "*" with the ip address of the interface you want to listen on
if you are sharing printer you should configure cups and which you can get to from http://localhost:631
if memory serves