NO, please do NOT "Complete Transaction" before your item arrives and you are able to verify it.
If the seller doesn't deliver your item within the "Seller sends in" + 1 day time frame, you will be presented with the option to cancel the purchase. See how you can cancel your order.
If the seller delivered a defective or wrong item or falsely claimed to have delivered, please hold and open a dispute by choosing "Hold Transaction" and describing the problem in the resulting text window. Be sure to attach any screenshots that support your case.
By completing the transaction, you are accepting the item and finalizing the transaction.