adding the main server will be a lot of work,,, i mean i will have to add all the users again and many other things
Windows 2000 was the start of AD. Add a 2003 box, make it the main, all the users will transfer over, then run a 2008R2 upgrade.
Since there is no upgrade path from 2000 to 2008R2.
You wont have to re-create users.