Since you are new to InfoPath and deciding to dump it anyway, I'd just do it with the convertor app. It's possible in InfoPath but you will probably be able to do it easier in VB.NET since that is your forte.
I'm not sure what data you are looking for - is it a secondary data source, or a "filled out" copy of the form with stored data that user input?
For secondary data sources (2DS), open the form in Design mode (Right-click the XSN and choose Design), choose Data Connections from the Tools menu, and click Modify on each of the data connections. In the wizard that pops up should give you some clues as to where to find the files.
If you want to be tricky, you can change the XSN extension to CAB and then extract the files. This can also be done by choosing Extract Form Files from the File menu when the form is in Design mode.
I hope this helps, let us know how things go!
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Matt Faus
InfoPath Dev Texas
Matt Faus / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge