EU VAT Refund question

Hey, I'm thinking of getting a MacBook Pro in Vienna, Austria soon, but I've got some questions about tax-free shopping. As a non-EU resident, do I have to buy the MacBook in person and then wait a few days for it to be delivered to the Apple Store? And do I need to be there in person to request a tax refund form? Also, any idea how much tax I can get refunded?