It's quite easy to remove excess wax or change the shape of the mouthpiece. Just briefly put the end of the didge into an oven at low heat or under a hot light until the wax becomes soft. This is easiest to do with a reduction coupler. To decorate your didge you can experiment with heating the PVC with a propane torch and bending it and flaring the end. It's hard to explain exactly what you have to do to get the right sound, but when it happens it's quite obvious.
Some people get it almost immediately and others have to experiment for a while before they do.
Anyone can learn it with a little effort. At first you'll probably only be able to do it occasionally and only for short durations, but with a little practice you'll see noticeable improvement fairly quickly. The short video clip will demonstrate the basic idea. The sort of sound I'm making with the didge off my mouth gives you an idea of how loose the lips are when you're making the proper sound with the didge. Before you play the video clip, be sure you've understood the text instructions.