Uninstalling & reinstalling shouldn't affect any data files, including templates. What it should do, however, is replace any faulty application files & restore damaged registry settings that a repair might miss. That said, it's wise to make backups of your data on a regular basis and especially before major system changes such as this.

Your backup software should have settings to use for ensuring folders containing Outlook files and the like are backed up. By Default Outlook.pst is located in:
C:\Users\%UserName%\AppData\Local\Microsoft\Outloo k

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]