Made the mistake of using underscores as hyphens. I have a few hundred page titles to update. Wondering what the correct method is to rename these, in terms of SEO? I would assume I keep a copy of the old file and make a new one? Keep the old one for incoming SERP traffic.. would I get hit for duplicate content on that? Ugh.
You can use 301 redirect by modifyinf .htaccess file... herez an article that might help http://www.tamingthebeast.net/articles3/spiders-301-redirect.htm
What he said. Just to elaborate a little you will want to redirect ALL your old underscored URLs to the new ones under the hyphen system.