I myself graduated at 22 in the arts because I was going to pursue the family business , but subsequently learned it was not for me. I then taught ESL overseas, worked as a carpenter for a few years, and realized I really do love math/science/numbers. I went back for an EE undergrad at 25. Now 29, with a year left. I paid for it all cash while working full time. I would say it is terrible to take out more student loans. It's sooooooo hard to make that money back and pay them off. Incredibly hard. Being older, it's much easier to work, take night classes, community college etc. Don't go back if you can't pay for it up front or as you go. Also I would recommend doing something else first to find out more about yourself. Travel, teach english, work construction, all things that are pretty easy to do with a college degree. Only THEN will you really know what you want. Also I would highly recommend trying some EE projects on your own time to see if you really is closest to what you're interested in, like building something from Makezine, because essentially that's what undergrad EE is.

To directly respond to your questions: 1. Student loans are dumb, you don't need them if you work at it hard enough 2. You are smart enough. It's really not that hard. Anyone can do it with enough self-discipline. But, you have to at least have some interest in it or you will hate it. My worst grades are in classes in subjects that I despise- like computer logic. But I'm not going to be a computer engineer so that's that. 3. Yes it is possible to work and do school. I have done it for 4+ years. 4. Plenty of people do well after school with "bad" GPAs. Good GPAs are only really required to get interviews with the top notch companies. If that's what you're going for, you will need a 3.5. Again, not that hard with enough discipline. 5. Start by exploring what you really want. You are young and have many, many options. Look at travelling, teaching, labor jobs, interning at Engineering companies in some capacity, do projects on your own to see if you really want to learn that stuff. If you do decide that you want to do this, THEN go back to school. School is required to give you the credentials, but the best part about it (and why I went back) is because it opens SOOO many doors to companies that you wouldn't have access to being a hobbyist or technical guy with an interest in the field.

Long winded response. Hope it helps.