No its a free inline update mate .
It does overwrite the whole os & back it up into a windows.old folder which you can delete or restore to.
You can keep all apps & documents though.
You should have been offered it now in the taskbar though.
Open the start menu search bar , type
Winver
& press return.this will tell you you your current windows version.
If its 1703 you're already on the creators version.
If not go here.
https://go.microsoft.com/fwlink/p/?LinkId=821363
& you can upgrade inline or create a boot media.
I would select to make boot media & select the iso file option.
You can then extract this in windows & run the setup.exe file
The reason for doing this is if you select the upgrade option & it fails then it has to...