to upgrade to High Sierra you can typically download and install directly if you are running the lastest clover zip etc.
i recommend making a usb installer too.
you can clone with dd if you know what you are doing - i used to copy my windows stuff using dd. i use carbon copy for my macOS copy
if you have modded your bios, you may be able to just put in the chip and go.
i use Atheros AR5BHB92 aka 9280 and it works OOTB - no extra kexts etc.
but it is just wifi. bluetooth is a separate chip .