Upgrading to Windows 10 preparation?

I have a Clevo P150EM (Sager NP9150) and I plan to upgrade from Window 8.1 Pro with Media Center within the next month before the free upgrade period expires. Is there anything I need to do or prepare before installing the update through windows update? Such as uninstalling things like my nvidia graphics driver?

I always prefer doing clean installations. After I upgrade through windows update, am I able to do a clean installation from an iso on a usb/dvd? Will it ask me for a key? If so...

Upgrading to Windows 10 preparation?