Ok , i assumed from. Your post you were going to use the disposable camera.
The second link shows a circuit diagram which should work.
A lot of my comments apply to hacking the cheap disposable camera.
The commercial flash should take care of all the dangerous stuff for you as they are desinged to be used with digital cameras.
I would however recommend that the flash unit is kept away from the arduino as a precaution.
Its possible the high current discharge could couple to unconnected pins etc on the arduino.