I have the same problem and am looking all over the internet trying to find the p/n for the plastic cog. My P7 started going haywire with zooming in and out...finally i opened up the thing. CAREFULLY, i detached and unscrewd the camera to get to the gear box, and inside saw the teeth on one fo the gears was gone.
If you have any info about the p/n or the name of that area...that'd be very helpful. I don't want to spend $300 bucks on a new camera when just a $5.00 part (most likely less than $10) can be used to repair.