That situation is very similar to what mine was like before I became a landed immigrant. The difference being that I was goign to school, and not working, but our status as visitor would be the same. The normal procedure for applying for landed status is to do it outside of Canada, meaning that he would have to go back to Australia to do so. However, since he has a common law wife, he can try to apply from within Canada based on humanitarian grounds. They would then process his application in Vegreville, instead of at the embassy of his home country. During this procedure he would be allowed to stay in Canada. The tricky part is how he would support himself while being here, since he's losing his job his work permit would be revoked and he wouldn't be able to work here legally - and I don't recommend working anyway, could be disastrous. The processing time varies from case to case, but for me it took ~10 months.
As for difficulty to complete the application... there's a lot of stuff to fill out, there's no question about it. Both himself and his wife, as his sponsor, would have to fill out lengthy applications and supply all manners of documents. If he doesn't have all the documents required, it'll take even longer. The only document that I had to specifically acquire was a statement from the Swedish police stating my crime record, or lack thereof. He will need such a statement from any country in which he's lived for more than 6 months.
If you have any other specific questions, let me know.
The above mentioned site is a good one to use as well. Another option is to get in touch with a lawyer. There's lawyers who specialize in immigrational law. A bit more expensive, but from what I've heard they usually know their stuff.