By the way, if you do not presently own an external backup drive, and are not taking full system image backups on a routine cycle, I beg you to go out and get yourself one now, and institute that practice beginning the moment after you have your machine configured as you like it after having done the reinstall.
This is one way you can preserve your data and your system as a whole. Then, if anything goes wrong, you have a "restore it and run it" solution that brings you back to what you know to have been a fully functioning system.
Take off-routine-cycle full system image backups any time you do a lot of software installations on your machine or you create a ton of new user data that you would not want to have to create again (or lose after uploading, if we're talking about photographs).