If you don't get a package from the seller by the time the estimated delivery date you were given by eBay (not some later date the seller promises) when you paid has fully passed, go to your Purchase History for that item, click the link for more options and select that you haven't received the item, then follow instructions from there. If you haven't gotten the item as described or a full refund after 3 days (but before 21 days) from doing so go back and you should find a link to "Ask eBay to step in" to get your refund.
You only have 30 days from that estimated delivery (again, the one eBay gives you when you pay--it will be in the email confirmation of your payment/purchase/order--the last few I've gotten were titled "Order confirmed") to start the process. Sellers breaking the rules on pre-order items (which require them to be able to ship the item within 30 days of payment) will try to stall you by promising it will be by some later date but that promise does NOT extend your time to file. If you already missed that deadline go to your payment source (PayPal gives you 180 days from payment to start its process, credit card deadlines will be set by the issuer).
