I made it without a PEG but it was not an easy path. I needed numerous IV hydrations and looked like skin and bones. The advantage is that you will have better swallowing function right from the start.
Beth Israel used to spray my mouth with a saline solution after every rad treatment. I also wrapped my teeth and gums in gauze before each treatment. That seemed to help. Best of luck. Keep up the fight and this all will get better.