How to add a new onepagecheckout step?

I need to create a new step in the OSC, within this step you will have two options with radio buttons, hire and not hire. if yes, the cart total must be updated with 1% of the total value of the cart. I already researched in several national and international forums, the closest I got was following this tutorial: link . But after so much work nothing happens. Does anyone know how I can do this?