I tried the night in the freezer trick to no avail. But I still finally made it to get the piston out of the slave cylinder. I disconnected the front left brake line in the wheel well and connected it to the slave cylinder with its pipe and a piece of fuel hose and two clamps (thread diameters are different). I then pressed on the brake pedal and voila, the piston popped out. It doesn't look that bad in there, but I still ordered repair kits.