Hi bongman, looks like you've got yourself a big problem! What about sending for repair?
Usually, the outputs (1 to 4) can be assigned to whatever outputs you want. 1 and 2 are usually the standard stereo outputs, with left as the mono output. 3 and 4 can be assigned as stereo L and R. If the Korg is the same as the Yamaha, then you can assign different effects to either 3 or 4 individually, assign different voices or the individual elements of one voice to either 3 or 4, you can assign different controllers to either 3 or 4 as well etc. But I've not used any Korg module. If the same principle applies, then that's what these 2 extra outputs can be used as.