I've done it, diploma and advance diploma over the years.
A cert 3 these days will cost you around $1000 - through tafe - if you have a health care card it will be much cheaper.
Make sure you do it through a registered training organisation. Consider doing a traineeship also, good way of earning a bit while you do it - you will need to do about 150 prac hours for the course so why not get paid while doing them.