Q, afaik you shouldn't need to reinstall anything if you do an upgrade from windows 7, there have been some issues with older programs but running them in compatability mode should take care of that if needed.
here is a link where you can get a windows 10 pro cd key for $14.00, i used them to purchase mine and it is legit and works, you will have to download the windows 10 installation package do an upgrade install and then activate it with the windows 10 key, but at least this should save you a ton of money on it
https://www.g2deal.com/windows-10-profe ... l-edm.html