Sailing is actually a pretty diverse field. There's a lot to learn, and a lot of choices to make about what to learn. E.g. Racing or cruising? Big boats or small boats? Keel boats or catamarans? Solo or crew?
That being said, you should be able to find an introductory crew course that will fit into 2 days. One day is likely to be a stretch since it's usually anywhere from 12 to 20 hours for the intro courses I've seen.
Here is one Sydney school I found that offers a beginner keelboat crew course in four 3-hour sessions. They could probably be persuaded to do that 2 sessions per day. Failing that, Google turns up plenty of results for "Sydney NSW sailing school" and I am sure one of them will be able to get you started on your sea legs.
Another option would be to simply charter a boat trip with someone who is willing to less formally teach you some basics along the way. Sailors are generally not shy about "showing you the ropes", especially if you are polite, calm, and attentive.