How to integrate marketpress and appointments+ enabling me to offer a different payment gateway othe

After some reading, I'm guessing I would have to install marketpress, set up each appointment page/service provider as a product where a customer would have to checkout after setting an appointment? When setting an appointment, would there just be a submit button that automatically puts appointment into the checkout cart?

We are charging a deposit to our customers for setting appointments trying to eliminate a lot of "no'shows." And we would like to use Authourize.net for all payments. Thanks.