NEED HELP REVERTING BACK TO OLDER VERSION

Hello, I recently upgraded WP to 4.0. I then noticed that my EPIC theme was outdated, so I upgraded… HUGE MISTAKE. I need to revert back to what I had as the updated version has totally changed everything… I tried deleting the whole thing and then uploading the original epic.zip file but it says it exceeds the WP upload limits. How do I go about doing this? Please help ASAP!!