It has not been made for about 20 years now, so they are difficult to find. Is your's dead?
You can replace it with a typical signal diode like a 1N4148, but you will need to try and figure out a way to mount it close to the power transistor heatsink. It is supposed to sense the temperature of the output transistors and adjust the bias as the transistors heat up.
As for your capacitor question, I assume that you are asking about the tantalum caps. The dot usually identifies the positive lead, but there is a marking style that uses a color dot to signify part of the caps value (color code). Are the caps marked with the usual number markings?