Would I need to register as a business of some sort over there, do I need to disclose where I am to customers, like right now I live in vic but have all items shipped from sydney??
No US registration or anything else required to sell there from Aus, all your taxes are paid to the Red Queen's men, no matter where you sell and ship your products from and to.
Marc's right! Just as long as you meet the requirements to sell on eBay.com then you can. You might want to read through a few things - Link hidden: Login to view