I'm far from an expert on this stuff, but I once had it explained to me that squealing brakes is caused by dust between pad and caliper, allowing the pad to vibrate at high frequency - hence the squeal. There are many different "anti-squeal" compounds available that are applied to the back of the pad to stop the squeal - try the googleweb for more info.

If the stealer is planning to charge you to "de-glaze" to cure squeal, I'd find another stealer.