Before I buy any tool, can you confirm for me that the contact info is stored in the .OST file?

The technically correct answer is that your "default" contact/calendar data is stored in the default data file for the profile. If you only have one email account configured using Exchange then the .ost would be the only place where that data would exist.

As for "before I buy any tool" - first thing you need to do is download the program of interest and run in trial mode to view the contents of the contact folder to the extent that the <eval> version allows.