Updating Site URL

Hi,

I’ve re-designed a site for an existing site. The new one I’m working on is on a different URL (ex http://test.com) from the live site (ex http://live.com). I would like to apply the live site url to the re-designed site. What would be the best way to do this?

Should I just update the dns so that the live site goes to the new one? And if so, do I need to update all the URL’s on the new site so that everything goes to http://live.com instead of http://test.com?

I saw a thread that said to go to Settings/General Settings and update the WordPress Address (URL and Site Address (URL). Would I do this before we updated the DNS?

Any help would be greatly appreciated. Thank you!