How can I protect my personal data if I need to have it repaired without trying to erase all of it??
Your solution is actually quite easy: Backup all your personal data to an external drive. (That's something we should all be doing in any case.) After your data is backed up, simply erase it from your computer. When your computer comes back from the repair place, restore your backed up data.
The easiest way to backup your personal data is to use commercial backup software, but you don't have time now to research, install and test new software. Instead, you can do this:
1- Make sure that all your personal data is stored in these folders:
C:\Users\your user account\Desktop
C:\Users\your user account\Documents
C:\Users\your user account\Downloads
C:\Users\your user account\Music
C:\Users\your user account\Pictures
C:\Users\your user account\Videos
This is actually how Windows was designed to be used.
2- Copy the contents of these folders to folders with similar names that you will create on an external USB drive.
3- Test a few copied files, selected at random, to make sure that they open and work properly. In particular, make sure that you made copies of your files and not shortcuts to the files.
Once you have finished making and testing copies of your files, you can safely erase the originals.
Incidentally, steps #2 and #3 are what commercial backup software does, only faster and more easily.