It's been 20 years since I trod that path. So take this info with that in mind.
320 hours isn't a lot for Darwin, think of Darwin as your step after you have at least 1,000 hours or so. You might have to start at one of the communities that a Darwin operator services. Most "intel" used to be acquired at the "Institute" bar in Darwin. I have no idea if it even exists any more. Probably need an ASIC to get near the place...
Any way, most folks get their first charter gig at Kakadu or Kununurra (WA).
Most folks who are keen are already "there" working in the servo or pubs waiting for a shot. As the peak season isn't until July-September, then the exact numbers required won't be known until maybe May or later. Contacts and getting a "work ethic" is what's required.
You may get more relevant advice over in the Dununda forum.