Need help in removing first domain controller in domain

I am having a single domain in my company. There are three more domain controller configured. Now I want to get rid of the first one. But I am not aware about the process of removing it. I need some help here. I think this would be much easier to do by using ntdsutil tool. But I am a bit doubtful in using this. Can anyone provide me a simple procedure of removing domain controller.

Here are few working link that will help you to remove the same. There is a complete process available in the below link that will guide you more information. You must follow the steps mentioned below.

Removing a Domain Controller from a Domain

Demote a domain controller