Email was hacked; what to do?

The only way a different email account could be set up is for someone to have access to your computer. Obviously, the repair place did - was this an authorized service provider? I would ask them. Or, do you have internet file sharing or any kind of sharing enabled?

Second, regarding bitdefender: such software wouldn't find anything like that - they may find a virus which is something different. And, read this and think about uninstalling that software (there are many other threads here if you search for it):

Is Bitdefender virus scan worth it?

There is no need to take it anywhere to "clean" it - you can easily do this yourself. You will need to have a backup of your files; then use internet recovery (press Command + Option + R keys during boot up); when you get to the Utilities screen, use Disk Utility to erase your hard drive completely, and then reinstall your OS. Erasing it would be the safest and easiest way to "clean" it as you will start over with a new system - you just need to make sure you have a backup of all your files.

You're welcome!