Welcome to the State and the forum. As far as are you legal to OC on your IL license, the answer is yes. You are completely legal to OC as N.C. does not require any type of permit to carry openly. Most of the stories that you hear about law enforcement is to show how uninformed some officers are when it comes to the rights of N.C. citizens and their rights to carry firearms.
Now, as far as the purchase of the firearm from your friend, I will let others respond to that as I do not follow that aspect of the law as closely.