I know how the IMEI works. The part I don't get is that you suggest that the warranty is transferable. That's not how it usually works, you need to produce a receipt. Anyway, I can try, that should not cost anything.

UPDATE
Encouraged by kimmo's post, I have opened the blighter and can report that:

1. It was dead easy (although only because I already happened to have the right screwdriver - Torx T5, same as for the N9, in case anyone wants to follow);
2. My speaker is speaking again
3. My NFC is not, but that's the least of my bothers

I did not do anything special: opened it, rubbed the contracts with a finger nail, put it back together.