Importing Geographies in existing instance - Considerations

Summary:

Geographies were not imported during implementation. The geocodes are needed for Tax implementation. During the initial implementation, only the Country was created; no States, Counties, Cities, or Zip Codes. This is an existing instance. We are trying to assess the tasks that would be involved or the implications. Or, maybe someone has seen this before?

1. Delete old geographies, which is one country with no hierarchy
   1. Impact on Supplier Addresses which have not had validations turned on to this point
      1. Is there a way to programmatically update the supplier addresses?
      2. Impact to existing Requisitions and POs
      3. Would there be an impact on existing Payables invoices?