Here's a great article about building the timer. It is setup for a camera that takes an external timer, release or intervaleometer. You will have to figure out how to make a release work with your camera unless you want to open it up and tie into the switch contacts. I personally would try a small solenoid attached above the shutter button and pressing on a spring that then pressed on the button. It should press on the button for about a second to allow the camera to focus and take the picture. You could do this with a servo or motor and gears but then you'll have to design a way for the circuit to reverse itself.