Welcome! You're going to find chickens are an absorbing hobby, and if you aren't careful, you'll end up with a couple of very fine pets.
Before you waste money on a heating lamp, read this thread: Mama Heating Pad in the Brooder. It's on this forum.
If your coop has ten square feet, it will be large enough for two hens, maybe three. You will need an additional thirty square feet in a run outdoors for the chicks as they grow. They will need outdoor time after a few weeks to flex their wings and little legs.
Reading up on all the chicken diseases can scare the wits out of a new chicken keeper. With proper care, most chickens will stay healthy and you won't need to worry about disease. But learning the behavior of your chicks and what's normal will alert you should one take sick. Their behavior will suddenly change. So will their poop. Learn to "read poop" and you will be able to see many early warning signs of illness in time to treat it.
It would be helpful if you would fill out your profile, by clicking on "My Profile" in the upper right corner of the page, and we can better advise if we know what region you live in.
