How do change name and is that enough

I'm not clear on why you need to change it. Is your antagonist based on a real person and you don't want them to be able to identify them if it is published later as fiction?

If it's a great story and you look to publish it as fiction, I would change the names. At the beginning of most novels, if not all, there is a small disclaimer about "any resemblance to persons living or dead is coincidental, etc".

I'm not sure what the rules are if you are publishing it as a memoir. I'm thinking most law enforcement agencies are too busy with other things to track down something from a book.

Save than Sorry

Yeah, if you want to really distance yourself from the reality of it--change all the names, the setting, and even eye color.

There was an author who recently published a tell-all story about criminal activity around here.

No one sued him or anything like that - they just shot him dead (the criminal world seems to work that way)! The book is selling rather well but the author is not going to benifit from any of it.