That is definitely a guineafowl. They do better with their own kind. Raising them together with chickens may be okay at first but within a year or two they’ll start picking on your chickens.
They have a weird way of working out their pecking order and it’s not the same as with chickens. Guineas will peck and pull feathers. But like I said, this is usually around a year or two during the mating season, but once it starts it usually never ends.
I love my guineas, but they are loud. How big is your area and how close are your neighbors?
They are great for bug control. Sorry they lied to get the one sold. They should have forced the last person to buy a bunch of guineas to buy that one too.
As far as eggs, they will hide their eggs. If you’re going to let them free range, and if that’s even a girl, she will hide her nest and you’ll have to search for it. But she won’t start laying til next spring.
As far as knowing if it’s a boy or girl, it depends on the call and it’s easier to tell at around 6 months, maybe a little sooner but for sure by then.