To your first question: Your dentist that will be doing the extraction is going to make it so that even though you are not asleep you will not be in pain. They will normally tell you to tell them if you do feel pain so that they can numb the area some more so that you do not feel it.
To your second question: Having your mouth open for a long period of time will be tiring I am not sure about it really being painful. Since you will be awake you can let your dentist know you need to take a brake and close you mouth for a little bit. That should help you some.