Yes you will generally have to pay GST on imports as the importer just as people who export out of Australia don't have to charge GST - check out para 34-250 of your 2003 Master Tax Guide.
Irrespective of whether you have an ABN, the purpose of the GST is to make the end user bear the cost - hence, you will pay GST as an importer but as it's not for a business and you're not GST registered, you will not be able to claim a refund in the form of an input tax credit.