Hello Brett,
They will only irradiate the area where they suspect cancer so not the entire chest.
I needed heavy radiation over a large area because I had invasive bc but my skin is the same, no color change. I had scarring from the surgery only.
However none of this was not an issue for me, the only thing I cared about was could they kill all the cancer.
It sounds as if you should have another appointment with the radiologist or a nurse in that dept. to answer your questions also there are supplements you shouldn't take during radiation, stay out of the sun, no cream on the area before radiation, etc....so ask about these issues also. Generally they give you a printed fact sheet, but you can also do an internet search that might prove helpful. Besides this site, a general bc site is good:
http://www.breastcancer.org/
The radiation will be at the same time daily for 5 or 6 weeks so you'll see the same people in the waiting room which makes it nice. It only takes about 5 to 10 minutes total and she won't be tired the way she was with chemo. Very tolerable.
Good luck,
Sarah