[jclos]

Well ideally there is nothing you could not learn on your own, given sufficient time and resources. It depends a lot on your university I would guess, so the best thing to do would be to ask older students who took CS classes and left. Not only the successful ones, but also the others, if only so you know what not to do. A good way to know what to do is to ask the people who are where you want to be how they arrived here. You should also ask professors for their opinion - they might not know about producing good software, but they almost always know a lot of stuff, including other students that might be able to help you.

Keep in mind though that CS is to Software Engineering what Physics is to Engineering. Getting a CS minor (or even major for that matter) won't make you a better developer, unless you are already a good enough developer that you can absorb some abstract concepts and reapply them in creative ways.