Hi, I am a qualified mechanic, did my trade back in the 80's when we did everything in house and never sent work out, we did our own engines, heads, gearboxes, auto trans etc etc etc I learnt so much, my boss was a hard ass but looking back it was good for me. I am now an automotive lecturer for Tafe and absolutely love the job, pay is great, conditions are great, equipment is insane (2 engine dynos, probably best chassis dyno set up in country, flow bench etc etc etc). Depending on where you do your trade training it could be excellent or just tick and flick crap.
Unfortunately the pay for mecanics is not very good, but if you are good it gives you good skills, and lets face it cars aren't getting any easier or cheaper to fix these days. I shudder when I see some bills people get as I fix all my own stuff and generally get parts cheap to knowing people in the trade.
It also gives you skills to do high end stuff, when I was younger I built engines for sports sedans and crewed for many hign end teams. You can build awesome stuff, time and time again I see absolutely crap workmanship coming out of shops, why pay when you can do it yourself.
You mention you're a girl, no problem, over the years I have taught many women and they are excellent techs, generally they give the guys a good run for their money. I wouldn't let that put you off doing what you like.
At the end of the day you have to do what you love. The job I have now is just fantastic, over the last 4 weeks I have been teaching 'Repair engines', the students have to run an engine then strip it and 100% measure, rectify and rebuild the engine and then it must run again, they also recondition cylinder heads, cutting valve seats and facing valves, setting installed spring heights etc, hone and measure blocks, balance rods and pistons etc etc etc, what a job.......................and then we usually run stuff on the dyno!!
We also have a week long 3rd year subject called 'Test engines using a dynomometer', the students go through using the chassis and engine dynos, they have to map out and tune various cars and engines using different ecus, they flow exhaust, intake and cylinder heads on the flow bench, they dial in and adjust camshafts etc etc...........and this is my job!!!! They pay me to do this stuff!!!!
Do what you love, as an apprentice ther will be times you will hate the job, due to pay and being low on the rung and maybe even treated poorly, but think about the end result.