Hello Leon,
What Ed said is on the money. I wouldn't be concerned by scare stories of Win10. This is going to be especially easy for you, as you have the CD-key on hand.
Doing a clean install, on a new SSD, using the Media creation tool (Win10 installer on a 8Gb USB stick) will being balance to the force, and much deserved relief for you
It goes without saying that more and more things work with Win10, ongoing. And as time goes on, use of previous versions will result in more exclusions for you. You have a great opportunity to start afresh here.