Ok, here's a blast from the past... anyone remember this image?
http://img27.imageshack.us/img27/5051/male2fem.gif
What I'm looking for is the two stories they were attached to - one where a boy wakes up with a vagina, and the other where a girl wakes up with a penis. I can't think what they were called, but they were two of the very first TG stories I ever read.