Maybe I'm naive but shouldn't it be enough to encrypt your disk with FileVault? Of course assuming that you don't hand over your password to the technician. Also logging out of iCloud would remove the option to e.g. lock or wipe the device remotely.
It depends. If you've bought your device from Apple, defects will be covered by them in this 2-year period. At least this was my experience in Germany. Two times I encountered a very helpful Genius that issued a repair although my 1-year warranty was up.
I have the same issue(s) on my third set of earpods and second case. It has gotten to a point where I don't want to buy another set of Apple headphones because I'm afraid this will happen again one day or another.
Listening to DJ sets (HÖR [0] is great) helped me with programming and other work related tasks quite well. My mind magically switches to focus mode :).
[0]: https://youtu.be/7FeqF1-Z1g0
[1]: https://youtu.be/zXXmhxbQ-hk