AD 2003 + DNS to 2008 R2 migration

I have One PC Runing windows server 2003 enterprise running AD, DNS, DHCP and WINS. I just got a new server running server 2008 enterprise and would like to Upgrade or migrate everything do that server. Where do I start? Do I migrate AD first or last? Any good guides or advice?
Please share good idea , i have downtime only 4 hrs