WIndows 2003 As A Backup Domain Controller For Windows 2000 Server

We use a Win 2K server for a domain controller.

We put up a Win 2003 server and it joined the domain.

Would like it to serve as a backup domain controller in case the PDC went down.

Found a link to http://www.tech-geeks.org/geeklog/article.php?story=20041223002509333

Not sure if this is all I need to do.

Not sure what this will do to the existing PDC. Will this be disruptive?

Not sure what to do if the PDC ever goes down.

Thanks.