It's not destructive at all and is also known as a non-destructive install where it doesn't affect your personal stuff or 3rd party programs, although it may default some of the apps such as your browser back to Edge if you are using a different one.
If you don't have a 1703 install disk then you can download the ISO from
http://windowsiso.net/Hover over Win 10 then 1703 and select Standard.
You can then use Windows USB/DVD Burner Tool to create either a bootable DVD or USB.
http://wudt.codeplex.com/You could also do a manual update to 1709 but I'd create a full system image first even though you get 10 days to roll back.
You can use the Update now button in
https://www.microsoft.com/en-gb/software-download/windows10You can also create 1709 install media from there after reading the instructions, as they differ depending upon whether you want to create a bootable DVD or USB.
If you do decide to update then check that System Protection is still On after, as it will remove all previous restore points.