OK, to add an external mic is fairly easy as long as you are comfortable voiding the warranty.
Again, you will void the warranty if you do this.
Remove all the screws from the lower case. Slide the case off.
Position the lens to it far most counter clockwise position and remove the screw holding the lens cover on. Unscrew the lens cover.
Unscrew the remaining screws holding the body together. Separate the case halves.
Unsolidier the existing internal mic.
Drill a hole the exact size of your external mic lead in the front left side of your camera. Drill through the internal shell as well as the external cover.
Slide the external mic lead through the case and soldier the leads to the board. Put some more hot glue on to keep the leads from moving. The center lead should be the hot or out contact.
Reassemble the camera.
Take the existing mic and solder on new leads to the male portion of the connector.
I found this tutorial after I modified mine...
http://www.youtube.com/watch?v=H8Q9gKT3d90
Good luck. If you built an airplane this should be a piece of cake though.