Just to let you know, the Paypal structure has changed, so you'll want to update the directions a tiny bit. You have to click "Classic View" for things to be in the locations you describe. Just wanted to let you know.
This page has been moved to http://www.trepstar.com/paypal-ipn-gateway.asp
So, if I use PayPal for orders, that means the customer's money is sent to my paypal account and then I am responsible for funding my TrepStar account so that the cost of manufacturing and shipping is paid for?