Answer to: Keyboard ReplacementWell, that was fun... Let's just say I'm never trying that again! Broke the backlight, now I'm just ordering a topcase. Screw replacing the keyboard.
Answer to: How to replace or repair the headphone jack?First you need an old broken logic board for parts because no one sells the audio jack. They run $30-45 bucks on ebay. Unsolder the headphone jack from the broken logic board first for practice, Remove your logic board (instructions here on iFixit) then CAREFULLY unsolder the headphone jack using a precision tip and install the replacement being very careful not to burn any of the surrounding components.