Hi there.
You didnt mention what operating system the workstations are using??
As for the firewall, there are some really good How-To documents for it out there.
http://www.linuxdoc.org/HOWTO/IPCHAINS-HOWTO.html
I'm not sure if the above is the latest doc, but it got me up and running, although some of the contents leave me behind.
[Edited by Wazza on 03-02-2001 at 04:59 PM]