Upgrade from Peer to Peer to Server

Well, the time has come, we have more users than P.c’s, as much as I can I have avoided the 10 con-current connections on Win2kpro on our peer to peer network. I am now needing to upgrade to a server based network. I have experience of low level administration but not installing and configuring a server. Our situation would be to upgrade to the newest server edition available, I already have a HP Netserver E800, with tape drive etc. I would like my client machines to be kept on Win2kpro. I am sure that someone will be able to help me with some general advice and do’s and dont’.
Thanks fo your time..
Ian