Changing Perma link

Hi,

I want to change the permalink structure from “default” to “date and name based”? I tried changing it from the control panel and when I refresh the front end of my blog and click a link, I get error messages… Can someone let me know if it is worth changing it since i have so many blog posts? and will i be successful at changing it without having error messages to stories already on the blog? Please let me know. Thank you.