New Cart CHECKOUT for Prestashop

I require a custom checkout routine for prestacart the mockup site is crude just -- planning stage however, my client has approved this checkout process. --------------THE CART HTML MOCKUP--------------------- <[login to view URL]> --------------THE CART--------------------- ********NOTE: Ignore the SUBMIT button ******** FOR NOW>> click the GREEN bar below it to go step to step .. IN REAL CART - clicking SUBMIT opens new window NOTE: if user makes error there will be the typical red warning message PLUS the fields not filled in will show in YELLOW box around to easily identify. if price range I selected is not suitable welcome to suggest change give me your range in PMB At any time by clicking on the bar user can go back to fix or modify the information they desire....without affecting other parts. ----- other mods------- <[login to view URL]> As you can see walking though there are other parts that I will have other module and template work upcoming If you click on middle of any page it goes to next step, the entire site is crude just -- planning stage ===== Possible options, if too costly to get done in prestashop I could use Satchmo a Django & Python cart or that slow PIG magento, your welcome to comment or suggest... not os commerce though