Welcome jon2lin!
The good part about this business is that we choose to do jobs one at a time, or sometimes in groups of shops. When that job or group is done, it is over and we can choose to do others or perhaps that first one again next month, or next year.
Some people do perform some shops and then decide it isn't for them. However, it probably isn't because they don't know enough about the business as a whole. Many others continue for years. I've been doing this for eight years and am still learning about it.
This forum is a great place to learn about the industry. But please don't get bogged down trying to understand everything to the most precise detail. It isn't necessary. If you want to start, find the threads and articles that point a beginner to certain companies and certain shops. Then do a few shops. See how it went and decide if you want to continue.
Let us know how it goes.
And have fun doing it.
Happily shopping Rhode Island and nearby Massachusetts and Connecticut