Wow! Great guide! I will follow these instructions carefully, and I will point to this post if more people ask about this.
Thank you both!
BTW... From your experience, should I get a plain 2,5" SATAIII SSD or a M.2 SATAIII SSD, each paired with relevant USB 3.0 adapter? I don't think there will be any noticeable speed difference; I was just thinking about power consumption to ease Raspberry Pi USB port, since I won't be using external power...
EDIT: Forget it. It seems that M.2 and specially NVMe drives run hotter and are more power hungry than old 2,5" SSDs. I just leave here my conclusion for other users.