How do I setup DNS and Open Directory for a network of Macs?

I have a Mac OS X 10.5 Server and about 10 Macs running Mac OS X 10.4/10.5. Right now they connect to the server through simple filesharing.

I’d like to get all the workstations to access directory services from the server but I for the life of me can’t figure it out. I’m very well versed in the Mac OS X but am not an expert in server or networking tech. The information I’ve found either doesn’t cover my case or is far too complex for me to understand. I’ve tried Google, Apple’s discussion forums, etc.

So is there a concise, simple guide that covers how to setup a Leopard server’s DNS and Open Directory services but doesn’t interfere with our existing routing equipment and network config? (I just want the Macs to look to the server for file access and other management features for now and not for email or networking services).