For those with the boot up issues, did you create a bootable flash drive per this link: 起動用USBを作成する方法
and THEN follow the install procedure for High Sierra at this link: macOS High Sierraのインストール方法
I didn’t replace my hard drive, but those seem to be crucial steps prior to replacing it.
This document is also referenced in a comment in one of the earliest steps of this guide. https://s3.amazonaws.com/ifixit-assets/M...
Absolutely great guide for logic board replacement. iFixIt.com was also great in overnighting a replacement to the first logic board they sent me because it was missing the fan connector. Love the warranty on their boards. Worth the extra money vs buying on eBay, etc.