yea, depends what ASE test you're taking...my vo-tech teacher is certified in everything but auto and manual transmissions, he said it was a lot of studying but barely missed any on the tests...just gotta study I guess...
As far as learning about cars..well, I've always had dirtbikes since I was 5..so that helped a little. My dad knows a little, my pap knows a little, my step pap used to be an inspection mechanic..my uncle Troy (yeahloh95) knows A LOT about cars, no wonder, he has a 500+HP 95 GT and did most if not all of his own work. I now am in my 2nd year of vo-tech for auto/diesel, where I learn a whole heck of a lot. But, I think the most I've ever learned about engines and how they work is when me and my friend tore my old 2.3 Tempo motor apart, down to the bare block, sandblasted some stuff, painted some stuff, pressure washed some stuff, and put it all back together. Did it all in 3 days for our senior project. Hated every second of it but now I'm thankful I did it, and now actually ENJOY working on engines.
If you wanna learn about cars get a junk engine, tear it down, and put it all back together CORRECTLY. Teach you sooo much.