Yes, you can easily convert your saltwater tank to fresh. Here's how:
Filter - no change here. You will have to do frequent water changes for the first week to flush the system though. With no animals in the tank, change all the water to fresh, and do a half water change every day for a week. This will flush the salt and decay from the system.
Substrate - this will need to be completely changed, as coral sand would not be good for axies. However, it can be used with some kinds of fish, most notably african cichlids.
Tank and Decorations - these just need a thorough rinse with warm water to get rid of any salt residue. Same goes for any other gear you might be using (filter intakes, spray bars, etc.)
Certain other gear from your saltwater tank will not be used at all. Skimmers, heaters, refugiums, calcium reactors, UV sterilizers, etc. are completely unnecessary. You may need a chiller depending on your local temperature. I see you are in Australia, and a lot of people there are having problems keeping the temp down in the summer.