training a great dane puppy?

I am thinking about getting a great dane puppy, he is 4 months old. I want to train him as well as I can when he is young, everything from general obedience, to taking walks, and being housetrained. I'm also worried that since it is a boy he will lift his leg and pee in the house? How can I prevent this?

I heard that if a male dog is neutered before a certain age this will prevent them from lifting their leg when they are urinating.. true? If so what age?

Thanks.