advice on ecart checkout pages

Hi, ok I am going to setup a local checkout via paypal and I don't want to use the wizard as I like to keep it as clean as possible with my own styling and functionality.

I just want to get clarification in case I have missed anything, so the website will have credit card payment built on the website (rather than going to a paypal external page).

here are a list of my pages and what server behaviors I will be placing on:

1. Checkout.php (this will only include a html form for billing and shipping details, on submit everything is stored in a session.
2. Checkout-Payment.php - this will only include a HTML form to capture customers card details and store in a session.
3. Checkout-Confirm.php - this is a background page that does all the processing using the session data collected from above.
4. Checkout-Success.php - this will then save all the session data into an order table on database as well as send out emails and display success message.

the Checkout-Confirm.php will include
Gateway Credentials
eCart Local Checkout
Authentication for PayPal Express

In addition if I include a PayPal button on the Checkout-Payment.php page I can include a secondary payment option that will redirect to Confirm-Paypal.php which will include the following server behaviours:

Gateway Credentials
Get Payer Profile from PayPal Express Checkout
Process Transaction with PayPal Express

The Checkout-Success.php page will include:
eCart Store Summary in Database
eCart Store Details in Database
Universal Email

Am I missing anything?