Domain user as Domain Administrator

Hello,

How do I change a domain user on Windows server 2003 enterprise to a domain administrator with all permissions the main domain administrator has?

What I want to do is:
At my office, the system administrator might resign and another one substitutes him. I dont want to keep changing the main domain administrator password everytime the system admin changes.
I thought of creating a normal user for the system admin, and giving him domain admin permissions. Once he leaves position, all i do is disabling his account.

You just have to open up the Local Administrators group on it and add the Domain Users group to the Local Admins group. Alternately you should be able to set proper access permissions on the application without allowing full control to the users. There's a drop down box that allows you to choose what container of accounts to use. Make sure you're using the domain as the container.

Thank you for reply Expertz

So adding the user to server's local admin group does it all? even logging in to server and changing settings of domain?