Changed title and lost blog

Hi, I changed the title in the Settings,and changed the url etc. Now the site is coming up with the content but no template or anything other than my text. I can’t get back to change the settings back to the original. If I click on anything on the page, or use my History, I get a 404 message – page not found. The site was DesignYourRetirementLifestyle.com/blog and has been changed to LifestyleDesignForBoomers.com/blog