agreed its good to have a trade to fall back on, its sort of like an insurance that you will always get employment.
ive been an automotive painter for 7 years now, and it has its good and bad points. its always rewarding to see a smashed up car roll in and have it looking like new again in a couple of days, it good to use the skills learned on my own cars too, and it keeps me active as opposed to sitting on my ass all day in an office.
chemicals arent so nice though, pay isnt great (our trade can thank insurance companys for that), does get a bit repedative after years of the same thing too. i made good money painting on the industrial side for a short time eg earthmovers, cranes, shipping containers and other massive shit. but thats far more enduring and messy (no-one i worked with was really in that for the long term).
but yeah if you are keen on the idea give it a go and see what you think, croydon tafe do good pre-voc courses that will almost guarantee you an apprenticeship somewhere and also give you an idea of whats involved with being a mechanic. and if you dont like it just leave and try something else.