Lovely part of the World, where you are, isn't it ? ...Now to the matter at hand...
One of those (way overpriced, in my opinion) travel adapters (that simply take the parallel pins of US mains plugs through to the equally spaced, but angled, Australian pins) will indeed run your G50 from the supplied Line 6 plug-pack when connected to our 240v 50Hz sockets.
Sadly, however, not only do those expensive adapters seem bigger than the plug-pack itself, but also it's been my experience that "wall wart" plug-packs have a nasty habit of slipping out of them at the worst possible moments.
Both of those shortcomings can apparently (ahem) be eliminated after about a minute of carefully re-angling the Line 6 "wall wart" pins, using a pair of long-nosed pliers, ...aah, ...er, ...um, according to that anonymous bloke in the pub.
That Powertech supply you've bought seems ideal. For the benefit of other Line 6-ers, the key things to look for in such a "replacement" plug-pack are
- A regulated output of 9 volts,
- A correctly sized output plug that both fits the Line 6 receiver and is polarised to supply negative (-) to the centre pin and
- The availability of at least half an amp (500 mA) of smooth and ripple-free DC for the receiver.
Whatever you end up doing to "localise" Line 6's supplied plug-pack, my policy has always been to have back-up power supplies with me, so I would never consider the relatively small outlay for your Powertech one to be anything but money well spent.
Oh ...and all of us started as "dummies" when it comes to this stuff. (And lots of other stuff as well...)