Two Nic one Server

[vahiiid]

Hi, I'll explain the network and then what I want to do.
I have a router which is connected to internet.
A cable from router goes to a switch and all other computers including a server with a Windows Server 2003 is connected to the switch so to share the internet connection and files.
What I want to do is to Connect the internet through my first Nic to the server and then connect the server via my second Nic card to the switch so everyone can share the internet connection and the files on the server.
I'm doing this to control the bandwidth usage of the users and block some websites as this is a workplace network.
As far as I know, I cannot do this on my current network as My switch is Unmanaged switch and my Router for internet is a basic D-Link DSL504t.

Please advice on how to configure the IP addresses, Default gateways, subnets, firewall so to keep the network protected and anything else necessary.

Thanks
Vahid