I have taken plenty of indoor volleyball games and I use Manual. I do not let my shutter speed be slower the 1/300. My aperture on my 55-200mm seems to work if I use 1600 ISO. However I don't have any other auto focusing lens. I have a 50mm which lets in the PERFECT amount of light, but the focusing is nearly impossible. Get to the gym early and shoot warm-ups to get your right shutter, aperture, and ISO down so that your not scrambling to figure it out and loosing valuable shooting time. OH! I almost forgot... DON'T FORGET TO MOVE AROUND!!!!!! I made the mistake one game of staying in one spot and only seemed to like about 3 out of 800+ shots taken.
I set up my camera for my mother to take pictures of me playing and she came up with these....
P.S. GOOD LUCK!!!!!!!!!!!!!!!! can't wait to see!
What position does your brother play?