To change the page type, you'll need to add a Open Graph tag to the page. You'll need to edit the Virtuemart Flypage template file and add the following tag:
{SCOpenGraph type=product}It will take Facebook a few days to 'see' the update, but you can use the URL Debug Tool to test what it sees immediately:
developers.facebook.com/tools/debug
Other available page types can be found:
developers.facebook.com/docs/opengraphprotocol/#types
Hope that helps, but if you need more information on how to add the tag, just let us know!
Thanks,
Alex