Swapping 2 domains

I have been searching the net and unable to find exactly what I am looking to do. Was hoping I could get some assistance. I have 2 domains site.com and site.org and I would like to swap the site and content on site.com to site.org, and vise versa. Is there a simple way of doing this that I am overlooking? If not, what would be the best way to tackle this? Thanks much.