First, this entire era of Hammonds was plagued with internal connector problems, though yours is a Japanese model and may be better than some US-built organs. So open up, unplug, clean and reconnect every internal connector you can find, one at a time. Then see what you have.
To play the pedals manually, make sure that none of the autochord/autobass buttons are turned on, as these will almost certainly disable the pedals. As for the volume pedal, chances are that it's either the bulb or the photocell receiver that's blown, so check both.
Usual caveats apply. Be careful inside. Though most of the electronics will be running on 12v or so, there are higher voltages present in the power supply and leslie units. And don't spend much money on fixing it as it just isn't worth it. You can get a working one of these for free or almost nothing. If it has real issues, cut your losses, dump it and get another - perhaps after having removed the leslie unit.
PS, just noticed you're in Oz. Prices can be funny over in Godzone, and finding a 'replacement' maybe not so easy.