Can disconnected earphone ribbon (step 7) be repaired?
I disconnected the earphone ribbon despite warning in step 7. Is there a possibility of repair (I'm guessing it is unlikely any adhesive would work) or replacement of the full mechanism?
Yes it's possible to replace it.
Using a magnifying lens you should be able to put the ribbon cable back in, using the magnifying lens to verify the bare metal portions of the ribbon cable are properly seated.
Super glue will work wonderfully, and should not be conductive (I have used some on electronics before).
If it fails, just replace that whole mechanism.