You can buy Turnabout here...

http://www.freemoviesondvd.com/index4a.htm

(scroll down that page until you find it)-all movies $9.25!!! Great selection. I looked ALL over the internet for this movie and finally found it. I did not know the title and had to look for the content LOL. I saw this late one night as a teenager.. long ago.. and I remember it was really funny. Can't wait to see it again!