The bulbs are 8V, 300mA. All three are in series, so if one goes, none light. But you won't find 300mA lamps easily, so use the 250mA lamps (but because they are in series, you will have to replace all three so that they are the same).
The stock are wedge, but Kenwood used a tiny crimp to connect the wire to the lamp leads rather than struggle with trying to solder or use a socket like some Pioneer receivers.