Well done on getting so many!
The thing with nebulae and galaxies is that they are quite faint and are extended objects. Light pollution and the moon will kill them off. Best bet is to wait a few days when the moon is past full and rises later (this chart will help to calculate
http://www.timeanddate.com/moon/australia/sydney )so you have more time before the sky is washed out.
M8 is interesting as it is actually very bright, even here in Colac it is easily visible with the naked eye. the problem is it is also very large, so the surface brightness is low and you need a wide field of view to get it all in. Trifid is smaller and fainter but should be possible.
You don't need to do anything to your scope, it is largely about getting the conditions right, although a light pollution or UHC filter may also help to improve contrast.
Keep at it!
Malcolm