Not an easy solution, I have a public school network with W2K and 10.2....To get/share usernames, passwords, home folders etc between systems took LOTS of research, Acitve Directory Schema Changes, and Netinfo configuration changes in order for both systems to read/write information back and forth.
10.3 Server is "supposed" to have these abilities BUT Apple has made this claim with 10.0, 10.1, 10.2 and now on 10.3. I'll believe it when it happens right out of the box.
Apple made us pay full education price for versions 10.0 and 10.2 and now offered a 3 year "protection" plan (for full education price) for any "future" releases of OS X Server.....
So basically we have paid full price for THREE server versions in less than three years......And Apple still hasn't lived up to marketing (performance and integration) claims from version 10.0