If I were to completely uninstall and reinstall Outlook or Office, will I lose all of my messages and settings?
Reinstalling Outlook won’t delete any email, contacts, calendar items, etc… just like reinstalling Word won’t delete any Word documents. In fact, it will leave most, if not all, your settings intact as well.
Uninstalling Office will not delete any Outlook data.
Backup before your proceed anyway!
Of course making frequent backups of your Outlook data (pst-files) is still a good practice and before you start it never hurts to make an additional backup. For step-by-step instructions to backup and restore Outlook data see; Backup and Restore.
Note: If you wanted to reinstall to reset Outlook settings, see; Starting Clean