Hi bellini3, thank you for your support.
The client was using cybersource with jigoshop (a wordpress ecommerce plugin), and now he moved to prestashop, so he want to use exactly the same payment gateway in prestashop. This is the plugin he was using in jigoshop: http://docs.mgates.me/cybersource/, so it seems that it would be the option 1) that you said.
Could you give an estimation of price and time for that? Also, I can send you the jigoshop cybersource plugin files if this would be helpful for you.
It's a VPS server, so it would not be a problem if a PHP extension is required (but I think that it was not required for the jigoshop cybersource plugin).
Also, could you give an estimation for the option 2), in case the client prefer this method?
Thanks!