I'm sorry that I provided so vague information, but I kind of wanted to fill in the blanks myself, and just get some general advice that I can follow-up on. Of course, I did not expect any consulting services for free. However, I realize now that I should have provided more information, in addition to not assuming that people can read my mind. Also, I'm not so used on posting on forums, and my experience in computers is in a different field; although the boss asked me to act as a kind of personal consultant when the actual external network consultants are brought in. After doing some more research, I think that I have a pretty good idea on what kind of setup we need.
Basically Im understanding that you are going to tell the actual external network consultants: "We need a network that will run Windows Server 2008 that will have 15 employees working on site. We have a server and conference room. Guest and additional visiting employees (what does this even mean I have no idea) need connection to the network. Wireless is important. Employees offsite should be able to connect to the network. We need a backup solution."
The question that first pops in my head is why do you need Windows Server 2008? Depending on your reply, we can move on to other aspects or get into why and why not a server running Windows Server 208 needs to be used for the reasons you just stated.
Id REALLY recommend you have some sort of plan and idea (a drawing like Budman gave you would also be awesome) and a budget. We still have no budget. If we have a dollar, we would tell you this is (close) to impossible. If we have a billion, we could have space to give you future expansion.