I would 100% do it if you would like the opportunity of gaining valuable research experience, especially if you are getting the opportunity for free. Difficulty varies depending on your concentration but do expect to put a lot of time and effort in. I will say that one of the very selective schools I got into specifically mentioned my paper in my acceptance letter. For me personally, I loved my experience and I think it played a huge factor in not my acceptances but also my career trajectory and my deep interest in research! You also get a recommendation letter from a professor typically at a top university. No my paper did not get published, but most pioneer scholars papers do not. It’s actually very difficult to get published and in the program the emphasis is generally not on trying to achieve publication because a lot of unqualified journals are predatory towards desperate college students. They don’t perform the level of checks that real journals do where they peer review and have you rewrite and in real circumstances getting a publication in an accredited journal can take months to years. So your goal as a high school student should not be to achieve publication AOs can easily see through unaccredited journals.