Qantas domestic sale is not much good if you want to travel NRT-DEL! JAL, Cathay and MAS can be very expensive compared to flights of similar length on Europe or USA, so the airpass can be good value.

My experience with OW airpass (South America) is that it is easiest to buy directly from the Oneworld airline. Perhaps you get lucky and find someone in Flightcentre who knows about them, but probably you will not.

If you are issued a QF ticket, then I would speak with QF to arrange it. They will hold the itinerary, and then you call back in a few days to pay when the cost is confirmed.