First Script: Need some basic skill help? Can you add an image with a click?

Hello, Im working on a project were you can replace people heads in a photo. Its for a project so its not supposed to be perfect. So far heres what i think the best steps to take are, but im not sure how to take the first scripting steps. How can i add an image with a script? How can i store a x y coordinates?

1. 1. I would create four variables and than store the XY cords of the the high point of the head, the bottom of the chin, amd the farthest right and left of the face.
2. 2. I would than add the image of the head that I would already have.
3. 3. If the x coordinates of the top and bottom are off kilter, I would rotate new head until = old face dimensions..
4. 4. I would also see if the width is too big or small and resize accordingly
5. 5. I would than resize the head so that the eyes would match up.

Thanks for any help you can provide!