31 PC + 1 Server...

Your hardware needs depend on what server and workstation OS you plan to use. Your WAN design will depend on your user count/traffic load from each site.

Truly need more information to assist.

ISP->Cable Modem->Router with NAT->Switch. Users' workstations and server connect to the switch.
To share one Internet connection among users, you need router with Network Address Translation (NAT). If you are looking to host any services (e-mail, FTP, Web, etc.) that must be available from Internet, you need router that also supports Port Translation. Most routers nowadays do support both functions and more. On a cheap side, look into Linksys. Great products of Cisco quality and low-end prices. Router must have DHCP enabled in order to supply IP addresses to the client workstation. Set up the server with static IP though. Regarding NAT - read here for starters: http://computer.howstuffworks.com/nat.htm

As BFilm says need more information.

you mention a connection to 17 nationwide offices? How? Over the internet? dedicated line? ISDN? What are the security requirements? individually and collectively? Is this a forest of domains? locally, how are you setting up the network? e.g. physical topology? are you grouping pcs in subnets by department/physical location?

It will looks like this:

Cable modem=>Router=>Managed Switch (you can divide Internet speed to the users - 31 users is a big amount for only 1MB inernet)=>Server and PC's

UPDATE: I just got back from a meeting with the IT guy for this Co. Here is the laydown. The company is moving the Admin branch of the office to a new location. They are going to use the same equipment as far as the Server, Switches, Routers and/or Modem.
All I am going to do is set everything up at the new location. My Boss and I are trying to seel them new machines, i.e. new PC's(theirs are about 2-3 yrs old) Just cloning the old HDD's to new larger HDD's. Hopefully getting a newer Server aswell...
Either way I haven't seen their machines, and I haven't got a reply on what hardware they currently have.
What I can tell you that might help is this: This particular office is the HQ for an oil company in Mexico. The other 17 locations are around Mexico and a few in the US. I am in the process of finding out the exact locations. They do have a Co. E-Mail that can be accessed over the web...using Outlook. I assume that each location has Domain according to that particular office's location.
In this project I am planning on setting up the 31 PC's into groups...all the Engineers and Admin staff in one group and all the support staff in another. I do know that there are about 3 Network Printer (The Big Ones) One in each group. The plants Manager and 13 Engineers have their own printers. So that is 14 Printers that are going to be shared and 3 Network Printers as well.
I WILL ADD MORE DETAILS TOMORROW...THANKS

ONE MORE THING: I beleive that they are currently running Win NT 4.0. Maybe upgrading to Windows Server 2003. Which Server OS is most recommended for this kind of International and local Network?????

Novell Netware will be a real good fit here, for several reasons:

* Do the remote offices have servers? Win2K3's with AD will consume a large percentage of your inter-office bandwidth just for domain replication.

* NetWare is licensed per user; build as many servers as you want, no additional licensing $$$, any user can acces any server you give them permission to.

* Branch office, Virtual Office, iFolder.

* Management via secure web connection.

* Windows and Unix connectivity out of the box

* Apache, MySQL, PHP, Tomcat integrated.

As others have laid out the basic ground rules and asked the right questions I'll just comment on the OS platform issue. I would stick with NT4 until you are sure that there are not some dedicated programs that will only run on NT4 and not on the newer versions of Windows.

You mentioned Engineers and that made me think that this is a specialized environment and most likely has specialized software that was written for the job but because of the limited demand for this software it isn't upgraded as time goes buy as there isn't any profit in this for the vendor. There are numerous specialized applications that will just not run on anything but NT4 Siteworks is a good example and these applications can not be migrated to another OS.

To keep things simple first move the hardware and get it setup and then start worrying about what can be changed and even then keep the old hardware running in parallel just in case there is some little used application that will not work on the new system. The other systems should be OK to change but be very cautious where engineers are involved as they do have some strange stuff running at times and since you have already said this is a specialized area it is better to keep things as they are until you are completely satisfied that they will run on newer OS.

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