Hi Ken,
The current fields which can be imported into Vantage via the built in .csv importer are: Title, description, author, date, slug, status, address, phone, facebook, twitter, website, listing category, listing tag, latitude, longitude (attachments). So yes, in terms of also importing rating data, this is currently not something you can do via the importing tool by default. The alternative to this would likely involve some knowledge of mysql admin, so yes, it could be done via the database side. I will enquire about how custom fields are stored in the database and will update the thread once I can confirm this.
There is no encryption which would prevent you from customizing the category pages. You may find the
AppThemes developer center for information about customizing our themes. Sitemaps are not generated automatically, but there are plugins which can do this. Thanks.