Bulk Reformatting of Wordpress posts

I have a site that was migrated from an old CMS to Wordpress. The posts currently have styling in them like the following: <p class="p1"><span style="color: #000;"><span style="font-size: 12px;"><span style="font-family: verdana, geneva, sans-serif;"> I need a automated way to remove styling of specific classes from the posts without affecting the formatting (headers, bold, links, bullets, etc). Start your post with your favorite fruit so I know you actually read this.