I'm sorry for your loss of Charley.
For the gender of the new puppy, I would keep an open mind and simply look for the best puppy, female or male. Kind of let the dog choose you. I originally was looking for a female when my first boy chose me.
I have 2 very strong males and they get along beautifully. It really does depend on the individual dogs. I don't think there are any rules when it comes to a perfect combination.
Neither of my boys marks in the house. Outdoors, they are leg lifters, but I could have discouraged that.
Best wishes in your search!