I'm using Gimp 2.6, and I'm trying to use the path tool to get this effect.

With this image:

I wanna use the tool to get only the woman and the rocks under her, so I can put another image in the background. Every time I try to use the tool, I mess it up, and it doesn't look right. Also, how would I make it transparent around it, so I can put something else for the background? I'm new to Gimp, and graphic art altogether, but I think it has something to do with layers, right?
Here's the tut I was using for the basic idea, but I can't seem to follow it right. Can someone help me out here?
http://gimp-tutorials.net/flat-photograph