Yes, all LED's are. LED is short for Light Emitting Diode. A diode is a "one way valve" for Electrons. So DC current will only run one way. When replacing LED's, look closely at the one you're removing. You'll see a flat notch on the base of it. Make sure you install the new one with the notch in the same position. If you install it backwards, it just won't light because the diode is blocking the current from flowing in the correct direction.
FYI: Radio Shack sells a nice little de-soldering iron that works great for removing components. It's a small solder iron with a red squeeze bulb attached to it to "suck up" the solder when molten. Copper solder "wicks" are NOT designed for delicate board repair - the solder can get too hot and lift traces from the board.
If you've never used a de-soldering iron, best to practice de-soldering/removing parts on a "junk" board before you move on to the board that matters.
Hope this helps!