Here's what I recommend:
1. Backup your files. It is a good practice you should do anyways, whether by an online service like Dropbox or Box or to CDs or a flash drive.
It will say it will preserve your files, and in just about every case it will. But things go wrong, so just prepare for that by following step 1.
2. In event of hardware failure unrelated to Windows 10, follow step 1.