Totally behind the ball here! I wrote this reply yesterday and forgot to post... just found it on my computer this morning! In any case, you've already received lots of info but am posting it now in case it helps at all...
My son's initial treatment was exclusive EN, using an NG tube, for six weeks. He was just shy of turning 17 years old. He had no problem with the NG tube. He was inpatient when admitted so, while still there, he was taught how to insert the tube (nurse did it with him 2-3 times??, and then watched him do it himself a few times). He learned quite quickly and, within a week, it took him only a few seconds to insert the tube himself.
He would insert each evening and ingest the formula overnight. In the morning, he would remove the tube (even easier and quicker than inserting).
There were a few glitches at the beginning - things like the tube creasing or coming loose, the sensation of having something in your throat bothered him the first few days (but, he became used to it after just 2 or 3 days), the noise from the pump annoyed him (but, you'd probably have the same using a g-tube??).
Because it was 7 days (nights) per week, instead of going to stay a friends' homes overnight, they just came over. He was very open about it all and often his friends wanted to 'watch'.
He wasn't allowed any food during the six week exclusive period (some GIs allow limited amounts of food) but he was allowed clear fluids. During the day, he took broth (in a thermos) to school so he could have lunch with friends. I also arranged for the school to keep freezies for him to also eat (he was allowed freezies, popsicles, jello). Evenings, he would have a bowl of broth. One challenge with using the NG tube overnight is that he was hungry by late afternoon/early evening.
Broth maybe helped slightly but really distraction was the only help.
Good luck!