It might be easier to just open up the sound files, silence them with audacity or audition, then put them back in and compile the apk rather than replacing them.
EDIT: Okay, I did that. It works on mine just great, but you may have to personally sign it. I'm not sure. And I had to uninstall the stock camera app, then install this one. All the noises are silenced though, so that's a plus