The answer to this question depends on what you mean by "become a historian". Do you want to be a history professor? Do you want to work at a museum as a curator or other type of historian? Do you want to be a librarian or an archivist? There are a lot of different career paths that fall under the umbrella of "historian", and you'll need different types of education and training for each of them.

Regardless of which of those routes you're interested in, you'll need at least a Master's degree in history for most of these jobs; for college teaching jobs (and many museum jobs these days), you'll need a Ph.D. That means you're probably committing yourself to a minimum of six years of postsecondary education, probably several more if you want a Ph.D. As with any career decision, you have to do a cost-benefit analysis here. Are the jobs that you'd be able to get worth investing that much of your time in education? Is it worth the opportunity cost of trading that many years of potential work experience for education?

And this is where I'm going to tell you what you probably don't want to hear but need to hear. The job market for historians is not good enough to justify the amount of time you'd invest in getting the requisite education to get those jobs. There are way more history MAs and PhDs than there are available jobs, and many PhDs are stuck stringing together low-paying adjunct jobs and contract positions despite all of those years spent in school. Universities aren't hiring many history professors, and most of the ones they are hiring are adjuncts and temporary instructors rather than permanent tenure-track professors. The museum and archive fields were already a much smaller slice of the pie, but those fields have suffered too, especially since COVID. It's possible that the situation will have improved 10+ years from now when you'd be looking for a job, but the long-term trends in the field don't support that idea.

So to answer the "should" part of your question, no, you shouldn't. By all means, take some history classes in college as electives if they're relevant to your interests, but don't commit to it as a career plan, because frankly, it's just not viable anymore. If I could go back and redo my educational decisions, I wouldn't have majored in history, and I certainly wouldn't have gotten a Ph.D., even though it worked out well enough for me, since I was one of the lucky few to get a good job afterward. I promise that most recent PhDs will tell you the same thing. It's just not a viable career path in 2022, and it's better that you know that up front rather than finding out the hard way like we did.

So this is a rather complex and deep question that requires some information on your part. The first part which is important is what do you want to be a historian of? Historians are a broad range of people with all having very different interest. Some study social patterns and development of issues such as urbanization, some study specific nations or time periods, ect. The list is vast and always growing of different things to be a historian of. While having a broad overview of most time periods due to academia requirements, I myself specialized in French military history of the 19th and early 20th century as well as firearms history. So you need to ask yourself "what is it that I like and enjoy in history?" and try to focus on that.

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The answer to this will point you in the direction of what schools and classes you will need to take. There will be general courses on world and US history but more advanced classes needed to graduate with something like a history degree will specialize into more narrow topics. For me, that meant taking a lot of classes on Napoleonic warfare and World War one. This is where choice of school will matter. Not every school offers the same classes and many will advertise what specific topics in history they specialize in. Getting my college education in Texas, many schools here have classes focused on Texas history or Latin American history. Classes are based off of the professors they have staffed as they need the experts to teach the subject. My school, while being in Texas, has a great military history program with world renowned professors in the subject which allows me to focus on that topic. A previous went to Texas state but they were pretty much solely Latin history and the grad program was lacking anyways so I transferred to a school that was better for my subject I wanted to learn. This will require you to look at what schools have what you want to learn and that you can also get into.

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As for what a historian does, that also varies widely based on where you are for your job. A historian of a small town might need to just look after historical landmarks such as buildings and make sure archival data is maintained. This would be drastically different from a historian for a world renowned museum or a historian that works for a government agency. Even large companies can hire on historians for consulting and looking after company data. Historians can also consult on things like media projects such as movies and video games. Again, this just goes back to finding out what you want to be a historian of. This in turn can help push you towards jobs in that field. Also the job prospects can vary widely based on what you want to do and experience and networking are super important. It's a reality that needs to be addressed but I try to always tell people to not let it dissuade you from doing what you like.

/u/sunagainstgold has previously explained why nobody should get a PhD in History.

I have previously collected answers on As historians how do you find sources and put them into context when writing a book?

See also When writing a historical book, where do historians find their sources? by /u/CoeurdeLionne, and /u/restricteddata

The subreddit FAQ has a section about History Careers and Education.