Spray penetrating oil on and let it sit. Even spray it on and drive the car to get the brakes a little warm. You can get a decent impact screwdriver for pretty cheap, but you should go and buy the screwdriver bits at Sears or something. I twisted off a few of the tips before I went to Craftsman bits. Also, go buy some spare screws, or even better replace them all, you will probably tear them up a bit. Take your time, allow for lots more time than you think it will take, replace both rotors on the axle and put on new pads. If you rub the used pads on the rotor and new pads, they will seat faster, it puts a small amount of the material on there and makes a noticable difference