My timing chain broke. It cost me $1800 to get fixed, I was obviously ripped off. Depending on whether you know people (cheaper rates on engine repair) you might be better off getting a 2nd hand engine (in good condition, warranty etc).
Six months after my engine was fixed, it died again, so I got a second hand engine for $1100 incl. labour. I was quoted between $800-$3000. Engine is still running fine after a year. I'm unsure on places in Melbourne (I'm from SA) but the YellowPages will always be your friend with things like this.
I'm sure to replace the timing chain the engine has to be removed or atleast lifted, not a fun job.
Hope this helped. Welcome to antrx.com, plenty of useful info!