No additional packages or installations are required on AEM 6.4 and later.Adobe Experience Manager Help | Getting Started with AEM Content Services - Part 1 - AEM Content Services Set up Which version of AEM u are using?
Bit difficult to explain from this as what's happening and causing the issue for me at least.Can you try to create same target config in OOTB We.Retail and see if its happening there as well.
model is the selector used by page model sling exporter.When you have custom implementation of component sling exporter, you have to give the path to component in repository and then use model.json on it