first off, for nearly everybody, win2k3 server is by far overkill in a home environment unless you have some sort of extreme and unique case. I also highly doubt you legally own th elicense to it Two, If you have a router, that will do all you need for DNS and DHCP in a home environment. Although you didnt state it, my guess is that you want a sort of central file storage, known as a file server, which you can use nearly any operating system, just setup a shared folder and your done.
If however I am completely wrong, just change your DNS settings in the win2k3 server or disable/remove the router and have your server do everything. My best suggestion would be to purchase "Mastering Windows 2003 Server" by Mark Minasi.. you will not regret it. I have his Mastering Win2k Server book and its incredible.