Update from Mountain Lion to High Sierra

Wanting to update my Hackintosh from Mountain Lion to High Sierra . Trying to see what the best way forward is. Don't really want to start from scratch. Looking to just do a simple OS update to my machine.

Specs:

-GIGABYTE GA-Z77-DS3H

-i5-3570K

-EVGA GT 640 (upgrading to Sapphire RX 580)

-Samsung 870 EVO 1TB SSD

-32GB RAM - Corsair Vengeance

Should I just follow the Tony Mac Guide for High Sierra install? Or is there a better walkthrough that would help, since I just want to do an OS update?

Also when should I install the new RX 580 video card I have? Before or after the installation of High Sierra ?

Thanks for any assistance!!!