You can find some information regarding uploading bulk data to Vantage
in this tutorial, however additional customization would be required in order to import data to custom fields. The "default" import .csv example file has the following fields: Title, description, author, date, slug, status, address, phone, facebook, twitter, website, listing category, listing tags, lat, lng (with a separate example file for listings with images. Hope this gives you some idea of what is required. Thanks.
