Got a white dead screen after an update

I had someone set up my website and use wordpress to write my blog & manage my site.
Tonight I click on the update for “Twenty Eleven Theme” and my screen went blank!
On the admin page, everything is in place, but when viewing the site there is just a blank white page. Here my question to you:
-Is there anyway that I can go back to the previous version? considering that I’m not familiar with coding at all? Can I fix this without paying someone to do it for me?

thanks.