Following up on my previous post I'd like to share how I eventually circumvented the risk of snapping the microphone connector socket on the I/O board. Instead of attempting to disconnect the mic (as suggested in this guide, step 14), I did the following: a. remove the battery, b. detach the right speaker, c. detach the microphone from the outer case (for steps b and c I followed the iFixit guide on how to replace a MacbookAir microphone). The advantage is that the microphone can now remain safely connected to the I/O board. Of course when reassembling the mac one has to reverse these extra steps (the microphone can be easily reattached to the case as it has a sticky side). I would strongly advise iFixit to revise this guide accordingly!
I agree, I found this to be the only critical step of the entire disassembly procedure: I snapped the microphone connector socket off the board despite applying a relatively gentle pull on the cables. Fortunately I did this on a dead MBair from which I wanted to get the display, but now I'm afraid of doing the same damage while installing the display on the target MBair!
Any tricks/tips would be most welcome.