It sounds like you are wanting to setup a pretty secure network. If you haven't done this before and you are going to be the one responsible for when things get compromised, I would strongly recommend some professional security/network consultation along with the great answers you can find here at EE.
To get started on your own I would recommend purchasing this book: (If 2003 server is what you will be running)
Mastering Windows Server 2003
ISBN 0-7821-4130-7
Here are a few suggestions that I would start with as far as research, web or book:
1) Active Directory Setup using specific user types and groups (OUs)
2) Group Policy management of the above users and groups (local and domain)
3) Create and manage file shares
4) Test before you deploy if possible
Sorry if this seems a little general but what you are asking involves about 40+ hours of setup by someone who knows what they are doing after you and your client have decided on what type of equipment and software you plan on running. It is always good to see someone wanting to get rolling on server/node networks but care must be taken, especially if you are using someone elses resources and are being trusted by them to keep their data safe.
Good luck and feel free to ask more questions.
