How close of a friend is it who you are getting the chickens from? If you know them well and trust them that their chickens are healthy then you wouldn't need to quarantine. I personally have never done so and have had no issues but you need to trust the person you are getting the chickens from...
The young ones are too young for layer pellets but are old enough to be switched to chick grower which is non medicated and the adult hens can eat that as well. Just make sure if the older birds are already laying that you have oyster shell out for them to eat for added calcium.