Hi aseeley,
Welcome to the forum. I have posted an image of the schematic showing that capacitor. I think there will be a delay before the image is available (it will be checked by mods). You should be able to find the a link to the image by clicking on my name next to this post.
As mentioned above, that capacitor is used for filtering the power supply (-12V line). It sits between the -12V supply and the power ground (0V). AC noise which appears on the -12V line will have a low impedance path to ground through the capacitor(s).
If the capacitor has leaked, there could be damage to the functioning of other components as well.
Without that capacitor, components using a -12V supply will receive more noise (possibly too much), and may not function correctly. This can cause intermittent failures.
The problem should be fixed. If you're not confident about fixing it, then find someone to help you. The capacitor should not be hard to find in a good electronics store.
Oliver
