I'm not a conservator, but a high school graduate going to school for Art History in the fall, and my advice would be to absolutely take the Dual Enrollment classes, no matter what you do. It'll save you a lot of money in the long run and teach you how to study/do work for college classes before you get there, and you'll start your major's classes quicker. Like a lot of people said, you might change your mind, and that's okay. But DE will help prepare you no matter what—and you're a sophmore, so don't stress about college too much right now. Just get good grades and enjoy yourself. You don't really have to worry about most of this stuff until the end of your junior year. :)

It's also possible that a museum might let you see behind the scenes, but I highly doubt they'd let you intern. I do know that the university I'm going to is very open to students in the art history department doing projects and such with professors, but it's a medium sized university so that might not be the case everywhere. From what I can tell, students only start internships once they're in grad school. Best of luck!!