Mass replace unique HTML

I need to replace this whole html that is wrapped in <p class="tumble"><p class="tumble"><p class="tumble">

    <p class="tumble"><a href='http://www.website.com/autologin.aspx?userid=4JLJufWQ%3d%3d&bookid=87' >

    <img src="http://images.website.com/images/P/image.jpg" alt="cover" /><em>Book</em> - Author</a></p>

with

  <p class="tumble"><embed src="http://daily.website.com/todaybook.aspx" width="258" height="320" /></p>

Is there an easy way to do this as a mass replace? The links and information inside the <p class="tumble"> are currently different by their all being replaced with one html embed tag.

Any ideas?