How do I upgrade the old Windows server in our small office?

We have a small office of 5 people, and we have a 10 year old server running Windows Server 2000. I just purchased a new server for the office and have installed Windows Server 2008 Foundation R2. I am pretty skilled with computers, but have no prior network admin experience. I was hoping to be able to figure out how to set up the new server by myself so that we don't have to hire a professional to do it, as we are on a very tight budget. The server doesn't need to do much at all, just basic file and print sharing, as well as one third party application (name isn't really relevant for now, it is a very basic app, no database or SQL or anything). I am trying to figure out how to set up the new server to eventually be able to swap in for the old server, but I'm pretty lost. Can somebody tell me what to do or point me to a place that has very clear step-by-step instructions of how to set up a new server where there is already an existing network? I have scoured the internet, but can't find what I am looking for. Again, I am very competent with computers, just have no real network experience. Thanks in advance!