Accept payments online using exisiting order form

General information for the website: Existing travel website
Kind of development: Customization of existing website
Num. of web pages/modules: 1
Description of every page/module: I require my exisiting order form to be coded to add up all selected purchase options, Provide a running cost and grand total on the right side of the order form and then the intergration of a payment gateway, merchant so we can accept payments online.
My preference is Sage pay but I am open to suggestions.
Description of requirements/features: Breakdown of work required:
Existing order form coding to provide an itemized cost for each selection chosen and a grand total on the right side of my existing order form in Step3.
See Existing form below
http://www.checkinpal.com/check-in-new.php

A payment acceptance gateway intergrating so customer can complete payment of order.

A copy of the order form is currently emailed to me and must remain this way.

A confirmation email also goes to customer and must remain this way.

Payment confirmation and details must be emailed to us too.
Payment methods: Credit Card, Paypal, Specific Payment Gateway, Other
Extra notes: