The silver piece broke of the mute switch rendering it useless and the phone can't be switched to vibrate.
Repair took about an hour. I went slowly and steadily through the teardown.
PERFECT! Take your time and be methodical and it is pretty straight forward to get as deep as you want into the iPhone internals. This repair requires the removal of a fair bit of the internals to properly reach and remove the switch.
iPhone 3G Replacement Battery
iPhone 3G and 3GS Mute Button
iPhone 3G and 3GS Vibrator
iPhone 3GS Replacement Battery