Recommendations for Audio / Visual Contractor?

I recently bought a house in Water Mill that had an elaborate audio visual system already installed, including wall-mounted TVs, ceiling speakers and individual keypad control units in most rooms and a stack of audio components about 6 feet high. But the sound and picture quality stinks and parts of it don't seem to work at all. I want to get a consultant to come in to look at the existing system to (1) evaluate all the elements to make sure they are working properly (and give me an estimate for fixing those that don't) and (2) teach me how to use it properly. Does anyone have a recommnedation for a reliable and honest service to do this? Do I need to find someone authorized to work on the specific brands, or does everyone work on all brands? Thanks.