I would like to add a bit of advice when it comes to isolating the battery from the board. As a repair tech, I recommend you insert a guitar pick next to the battery connector, rather than wedging something directly in between the battery and the connector, as you run the risk of damaging the connector. I see this happen fairly often amongst new techs and DIY-ers. If the battery connector does get damaged, it may result in the device not showing proper battery percentage (as in its a 1% all of the time) or the device may not power back on. If it does get damaged, it is completely fixable. But that should be carried out by a someone skilled in micro soldering.

Can the TouchID keyboard be purchased separately if the original seems to fail? I’m looking on Apple’s website and it doesn’t appear to be available, at least for the time being.

I would like to add that you’ll need a special tool to read and copy the serial number to the new Taptic Engine so that it will provide proper feedback.