The Microsoft TechNet article titled “How the Active Directory Replication Model Works,” at http://technet2.microsoft.com/WindowsServer/en/Library/1465d773-b763-45ec-b971-c23cdc27400e1033.mspx?mfr=true, includes information about Active Directory replication.
The Microsoft TechNet article titled “Appendix of Functional Level Features,” at http://technet2.microsoft.com/windowsserver2008/en/library/34678199-98f1-465f-9156-c600f723b31f1033.mspx?mfr=true, includes information about Windows Server 2008 functional levels for Active Directory.
Chapter 3, “Group Policy Basics,” includes information about configuring local Group Policy Objects.
Chapter 5, “Group Policy Processing,” includes information about how Group Policy processes settings.
Chapter 12, “Group Policy Preferences,” includes information about the Preferences settings in a GPO.
Chapter 15, “Troubleshooting Group Policy,” includes information about how DNS can affect Group Policy application and how to troubleshoot Group Policy replication issues.