The only way to really tell if the pad material is alright is to take the wheel off and get in there. You may see the front side pads looking ok but the backside pad may be under spec or rubbing the wear indictor. If the pads look ok and have good material across all sides, you can get some anti-squeal at any auto store. You apply it to the backside of the pads to help quell vibration which typically can cause the squealling noise. If you're going to take it down to check it out than you might as well make sure the pistons/seals are ok and your slides are well lubed. Clean it all up with brake clean and slap it back together.