Don't do an automotive as a profession, it pays **** all.
But if you're still in the midst of your apprenticeship as a plumber , you'll probably still be eligible for government subsidies for Cert II in Automotive Mechanical at TAFE, this is basically the entire first year of schooling for a 1st year apprentice LV mechanic, you could do it concurrently with your Cert III in plumbing.
It'll cost you **** all and you'll cover all the basics, 'back in my day' a decade ago when I was going through the system that first year included rebuild on a 5sp manual gearbox.
It'll give you everything you're asking for and how to do it safely for around $1500 bucks with the subsidies.
The catch is you have to do it before you get your Cert III otherwise you're not eligible for government subsidies and it'll probably cost circa $10K at that point
If you go this route make sure it won't **** you on extra certifications at a cert II level for plumbing, with us auto tradies we did this to get our Cert II in automotive refrigeration for **** all, it basically only cost us a couple hundred bucks, the guys who did the preapprenticeship cert II prior to starting their apprenticeship got stooged and ended up paying a couple thousand bucks for their AC certification because it precluded them for government subsidies.
This is also a good option for any of you oldies who have certifications that predate the universal student number system implemented circa 2014, your qualifications don't exist on the system so you could probably go do some heavily subsidized TAFE courses in something you're interested in courtesy of Australian tax payer