The hair loss at the base of the skull may be a surprise (exit radiation), but as many have said it is not likely to be permanent. Depending on your radiation schedule/area you may even get your beard or at least some of it back.... but it will take time and may look funny and even less grey. The radiation damage to your skin/neck also depend on the radiation dosage you get on your skin and how sensitive you are. In my case this has not been an issue; once the radiation stopped the red went away and other than a lack of tone the skin seems normal enough.
My mustache came back Charlie Chaplin style... to my great dismay. Given some time it has now filled in and my initial resolve to do something about it was not necessary (and would have been premature). The take home message is all of this needs time and you must be patient (which is easily said).
M