My first car was a Grand Am, 4cyl, when I was 17 and it made me start reading on Grand Am Owners Club about mechanical stuff... I had no idea how cars worked or what parts were involved or how anything was put together, I had rarely even seen under the hood of a car. I got the idea to change the spark plugs on it... I took the cover plate off and saw what I now know to be the spark plug wires... couldnt figure out where the plugs were, panicked, and put the cover plate back on before I broke something... I even made one of my friends do my first few oil changes.
I had that car for about a year and then I got my first GP, NA car... that's the car I did most of my learning on. I learned how to efficiently do an oil change quickly without getting dirty, learned spark plugs, which was easy but way more involved than a 4cyl motor. (I laugh and feel embarassed when I think about how scared I got about that, and how easy it is in reality, lol.) I did my first mod which was tearing apart the stock intake and fabricating my own intake... removed the factory downpipe and installed an aftermarket one, then I removed the front exhaust manifold to do a plog... the most involved job I've done so far was the hv3 installation which is just taking the plenum off, removing the factory insert, putting the new one in and slapping it all back together. Made some mistakes along the way that taught me what NOT to do or how to do things efficiently... tricks and little ways of doing things that prevent headaches later or just make things easier.
I repeated the intake, plugs, downpipe, and plog when I got my comp g and now I have those jobs down to a science... the first time I did the plugs on the NA car, it took me like 3 hours to do the back plugs, second time I finish the whole job in under an hour, oil changes take me 10-15 minutes normally, Im gunna be doing rockers and lim gasket soon so that'll be more experience... Im also in the process of redoing the brake lines on another car, but I never would've had the confidence to do any of that if I didnt have this forum to read on and get advice or help when I needed it, I had many panic moments where I ran in and hopped on gpf for help, lol.
In between the NA car and the gtp, I got a job at a parts store so I learned a LOT there, too.. you tend to grasp things quickly with a sweaty, angry redneck staring you down on the other side of the counter...
Point being, 95% of it is getting your hands dirty and learning by doing and seeing, the other 5% is a combination of discussion with people who are knowledgable and reading reading and reading. I started off being absolutely helpless, but between this forum and the other communities around, and getting out there and actually doing the jobs I feel way more confident in my abilities now, and you'll grow too if you want to.