I spend a fair amount of time on Hardline, mostly trying to learn from others' experiences. I usually prefer to keep my opinions to myself, but I read your original post and thought a response was appropriate as I was in a similar situation just a few years ago.
After I graduated high school, I went straight to college. It was a disaster! I achieved a 0.25 GPA my first semester and had a similar performance the following spring. The problem was... I wasn't there because I wanted to be, but rather, because that's what my folks expected me to do. I can say with certainty that that's the wrong reason to go to college (or do anything for that matter).
So, I moved back home and found a job working at a tire store. I did that for a time plus a couple of other short-lived jobs before I got a job changing oil at a GM dealership. I enjoyed it enough to stick with it and work my way up to a full bumper-to-bumper technician. Almost ten years after that first day on the lube rack, I decided that turning wrenches was not what I wanted to do for the rest of my life. The hard part was making the decision to leave my comfort zone of earning a decent living to do... something else. I took the leap. I started working at a small sheet metal shop thinking that fab work is what I wanted to do. It wasn't easy work, but it was a change of pace. A few months in, I was working on a job and some question came up about a drawing, so I asked my boss. He responded "I'll have to check with the engineers.". I thought to myself "What do the engineers do?". Shortly after that I began reading about the field of engineering and discovered how broad it is. I began looking back on my life experiences and considering my strenghs and aptitudes. I wanted to be an engineer! Thinking back, it seemed like an "ahh-ha" moment, although that likely spanned a period of a couple months. I talked to my wife about going back to school to get a degree in mechanical engineering. Luckily, she supported me. In fact, her exact words were "You're not getting any younger!". So there I was, 33 years old, about to be a college student again. I worked hard and put all my effort into learning as much as possible. The difference this go-around was that I wanted to be there, unlike before. (It makes a difference!) Well, 3.5 years later I walked out with a BS in mechanical engineering at 36 years of age. I landed an internship my senior year which turned into full employment upon graduation. I'll be 38 next month, and I work as a mechanical design engineer for a company called Molex. Things could change down the road (and they probably will), but I certainly love my career path at this point.
You're doing the correct thing by reaching out to others and trying to learn about various careers. Whether it's engineering or whatever, I encourage you to follow your dreams. Do the things for which you have a passion.
I echo the comments of others in saying... it's never too late to get started.
Best of luck on your journey!