Help and Advise for a novice

I have set up a small p to p network using win 2k pro o/s at my church and have a need to share a app program with 12 users on five terminals. I am a complete and total novice at network admin! the program needs to be accessable at all times as users come and go. how can I accomplish this with the least cost and and the limited knowlage I have. I would also like to administer the network remotly if possible. I have access to win2k server software but not sure if this is the way to go as I am confused about domain servers and file servers and such. Any advice will be welcome ps I am not afraid of challenages e-mail bobkamna@mindspring.com