I downloaded a custom ROM for my Samsung Captivate phone that is a variant of 2.2.1. Its version of the Camera allows me to use the power button to take pictures. I decided I want the stock camera without this feature. Is there a site from which the default camera.apk is available for 2.2.1, or for that matter, other apps?
So I just looked at the firmware for my Samsung Vibrant, you don't actually need to mount the image -- I was thinking of the recovery image or a nandroid backup. The firmware (ROM) should be in a zip file, which you can open up and go to
You can check out my answer to another question for info on mounting, but you shouldn't have to do that :)