Another Option is to go directly for an "In-Place Upgrade". That will re-install Windows, letting your Files, Documents, Programs and everything else intact.
That would be a good option, before you lose a huge time trying to fix things.
Have a look in this tutorial how to Repair Windows :
Repair Install Windows 10 with an In-place Upgrade - Windows 10 Forums
EDIT : For Testing purposes, to see if is a Software that is causing that long Boot time, try a "Clean Boot".
Here how to:
Right Click on Start > Run and type there MSCONFIG, press enter.
In the window that will pop-up , check "Diagnostic Startup", press apply. Now see if boot is much quicker.
Another possibility, in the same MSCONFIG windows is to go to "Services" Tab, check "Hide all Microsft services" and the "Disable all", after press "Apply", reboot and see. Do not forget to put this settings back to its original settings.
Another thing you could try is disabling all "Startup" Software. Press Ctrl+Alt+Del > Task Manager >Start-up and disable all items there. Reboot and see. After testing, do not forget to restore this settings.