I'm 20 and I just had a reversal surgery of my ileostomy 4 months ago. I had the ileostomy for 20 years (since I was a week old). As for the gas filling up, there is somethign called a charcole patch..I think that's still what it's called but what you do is you put it on the upper part of the bag (where the gas endsup) and you put a pinhole through it and the bag. The air that goes into the bag is released through the patch but because of the charcole filter, there is no smell.
As for the noises, boy do I remember that. I used to give myself stomach pains holding in the gas when I was around people. But to be honest, I don't think there is a way to stop the noises. Now that my ileostomy is gone, I still fart and there's still embarassing noises!! The only thing that's worse this way is there is now a smell that comes out with it! hehe. So I don't think there's a way to get away from farting noises but I used to do little things like hold a pillow or something over my belly to try and muffle the sound..or the good ol' cough-while-you-fart trick to try and cover the noise . Hope I was of some help! Keep in touch.