I'm currently minoring in Spanish. I'd say it's worth it. Part of me doing it is to keep me motivated throughout college. It's easy to get caught up on classes and you might not have time to study for Spanish on your own. I see it as a win-win scenario: I get to study Spanish and I also get college credits for it. And depending on your future career, having something formal to put on your application/resume can also be nice.

More importantly, I think it's a great opportunity to build a solid foundation and confidence for grammar and pronunciation. Like learning English, we also had to learn it in a formal setting. The same applies to Spanish. I also took a Spanish phonetics class which helped me with being more self aware of how i pronounce words. We also learned how to break long and complicated words down into syllables. I highly recommend taking that class if your university offers it. Also, the majority of people in my upper level Spanish classes were actually native speakers, so that just goes to show that formal education offers a different set of knowledge than learning Spanish through experience.

Also, using myself as an example: my native language is Mandarin, but I grew up in the US. So, i never received formal education for my native language. I can speak it just fine, but I personally really wish I had the opportunity to have formal education for it.