Just get a router. Any advertised as a Cable/DSL router will work. Set it up according to the instructions, but the network connection coming from the wall will be used in place of the modem. Then register the MAC on the router with campus IT.
As long as you plug the port from the wall into what is labeled as the WAN port, or Modem port, on the router, then the campus IT will see it as one computer. The router will hand out DHCP info only to computers plugged into the internal, or LAN, ports - commonly refered to as the ports "behind" the router.
This will have no detrimental affects on the campus network, however if you have problems you will have to troubleshoot them yourself - I'm guessing not a problem since you are posting on here.
As a bonus, this will also protect your computers from other computers on the campus network. Also, you could get a router with built-in wireless and use your laptop wirelessly - just be sure to disable SSID broadcast and add a WEP key so others in the dorm can't leech off the wireless.