Yes, this is correct, create the pages with the wizard, then apply your design to them
like i said in my previous response, the wizard is intended to create the pages, not to make changes. If you need to edit the pages after being created you use Dreamweaver.
When the wizard creates the pages, it adds the HTML code and server behaviors needed for the selections you make. you mention changing the settings for storing the orders, you would not rerun the wizard for this, you would edit the store order summary and store order details server behaivors that wizard added to your pages.
for paypal pro, you would find these server behaviors on the confirm.php and pp_confirm.php pages.
open one of those pages, open the server behaviors panel (Window -> Server Behaviors), locate the store order summary behavior, and double click it to make changes, or make the changes to the store order details server behavior if appropriate. do the same on he other page
it almost seams like you are not reading my responses. I addressed this in my last reply.
You don't use the checkout wizard to turn sandbox on and off. to toggle sand box on and off, and to enter the sand box credentials, you use the WebAssist -> eCart -> Gateway Credentials interface.
this interface allows you to set the live credentials and the API credentials for your site and allows you to toggle sandbox on and off.