It's pretty simple to at least get the login authentication working. You just have to go to the netinfo application (I think) and find the allowable authentication mechanisms. If you are running 10.3 you should see an active directory option. You add the machine to the domain, and I believe you have to set a specific DC for it to autheticate against, and then you can login.
If you want more specifics PM me and I'll try and check on how our macs are configured tomorrow at work...
Gaidin