2/. Now the fun stuff begins.
First find a pair of sunnies to suit the background image.
Remove the background (as you have done before - copy paste to a new image the same size, with a transparent background. Using the magic wand, the eraser and possibly the rectangular marquee tool.
Copy paste the original image over the transparent image and save as a Compuserve GIF or a PNG. Both these have clear backgrounds.
Resize the person to the background image requirements.
Copy/paste the image over the top of the background image.