The motor is out of the car, so it should be easy.

A big-@ss wrench wouldn't get the job done. I'm tempted to hit it with an impact, but don't want to bust it. Is there a special tool for removing it?

 

You should try a socket. I've never had a problem removing them before, even on 100K+ miles cars. Also try some PB blaster or some other rust penetrative stuff if that is the problem. Don't hit it though, you'll probably end up braking it.

 

I second the socket idea. I'm fairly sure it's a metric size, I just forgot which one.