WOOOO he's fired. That's some great news right there.
Now his replacement. It appears Klopp has ruled himself out, but if I were in charge at United, I'd throw every single thing I have at him to tempt him to change his mind. He is the perfect choice for Manchester United and he has the supporters backing ALREADY. Everyone wants Klopp.
If he truly isn't available, I'd go for Simeone or Van Gaal. I'm not the biggest admirer of Van Gaal but he is a world class manager and does bring some fear factor along with him. Simeone has a philosophy which I personally enjoy very much (like Klopp), but I'm unsure if the current players can even play his philosophy.