setting up os x server as a proxy server

Does anyone have a good link to a tutorial on how to set up OS X server 10.4.* as a proxy server as well as a file share server for a small lan?. I want to be able to restrict my users(students) to only about 4 or 5 sites and block the rest by default. I will also be the router for this lan giving them fixed ip's. If this post belongs in a different forum please let me know.