lorax - 2:41 pm on Jun 12, 2012 (gmt 0)

There is a handy plugin called Redirection that can do the redirects for you. Just making the move won't cause a penalty per se but you are likely to see ranking change while the SEs figure out what you've done. I suspect that if your site has a solid ranking now the pages will return pretty close or better then before. Providing you make sure to follow through on the details.