(#1) Modify the “wording” on the 2 payment receipt emails sent by SunShop cart (the “customer” copy . . . and also “merchant notification” copy). No fancy formatting . . . just changing the wording.
(#2) Configure the email settings in the Sunshop control panel, to make sure that the customer gets a copy . . . and also I (merchant) get a copy.
(#3) Configure a “Failed Transaction” email message (I don’t know what it’s called) . . . to notify the customer in cases when an attempted transaction failed (“Your order was not processed. blah, blah”).