Yes you do format a partition individually, without affecting other partitions on the drive.
Outlook stores your data in a .PST file. Do a search for files with that extension and copy them as a backup. Alternatively, from the "File" menu, select "Import & Export" which launches a wizard that will guide you through exporting your "Calendar" as a .PST file. If necessary, you can subsequently import this .PST file to restore your Calendar (as it stood at the time you exported it).