Noob setting up DHCP, DNS using Server 2003, 16port switch and wireless rtr

Hi, I am really stuck. I have a few hours to get this up and running before everyone comes back in the office 😐 What I am trying to do have Server 2003 act as dhcp, dns, and file printer server. Right now I have the external modem connected to a 16-port switch which connects the server and all clients. I can’t get the DHCP to work. I have internet on the server but cant get any other computers to aqcuire local IPs. I also dont know if its better to have the modem go into the router then to the switch or have the server connected directly. I only have one NIC card on the server. PLEASE HELP!!!