NT Domain and Win2k3 domain existing, how to make one win2k3

I have two working domain say ABC NT domain with file,print, vpn servers running on windows 2000 and an other domain windows 2003 (in the same forest, using the same DNS) say XYZ with exchange 2007 running. User log to NT domain and work for emails they log on to windows 2003 with same username different password and access mails. Now I need to move migrate from NT to windows 2003. what are the steps to be taken. If I join print server to new Domain will i have to reinstall all printers on server and desktops. how do i join file server to new domain, will it lose all shared permisssions and how do i take care of VPN