How to extend and rearrange eCart's checkout pages?

I have spend the better part of a day trying to customize the checkout pages for my website. My website uses the UPS shipping module. However, I would like to emulate other websites, like IKEA.com where the customer first types in the billing and shipping address and on the next page this results in the shipping calculation. After the customer knows how much the shipping will cost then they can enter their credit cart details and get to a final confirm all details page. I made a lot of progress only to be stumped after the transaction is completed. PayPal does not enter the email address correctly. The recorded email for the customer is: invalid_email_supplied@PayPal.com.

Obviously something is broken here despite the successful transaction. I am not a PHP programmer so I am basically hacking code around to make it all work. If anyone has any experience in extending the checkout process beyond eCart's default 3 page checkout process I will be grateful for any advice on how to make it all work.