Making a new step in the order process - Help needed

[JSHD]

Hello,

For a particularly certificating of my site i need to make an new step in the order process: An overview of the previous steps. ->products, prices, payment en shipping method, deliver address and some extra options, including an 'agreement' box for the terms of conditions.

They don't need to be directly editable, but it should be nice if a link is placed, where they could go back in steps.

Now i need some help to start up.

Can you guys tell me in what files i have to be to edit/add this?

For the experienced prestashoppers, can you give me a grade of difficulty? 1-simple/10-impossibly.

Hope to hear from you, Greetings,

Jos