Reinstallation

I had a corrupt functions php file in my theme. Our host replaced it and now it is saying that Genesis is a problem.
How can I reinstall both Genesis & the theme again or is that a StudioPress question?

We do have a backup of our website that our host can upload. Is it best to just start over or what is your suggestion. I am learning as I go with this so I am not well versed in this.

Pam