Dont bother with course advisers and course plans if you know what you're doing. Yes, they're helpful but those kind of services are more helpful if you have no idea whats going on or where you are going. If you put a few hours into learning the requirements and handbook + planning stuff out, you dont really need them.
Usually, all you *really* need to do is fulfil the requirements before you graduate. They go through a check-list to make sure you've done it all before you can graduate. In the interim, it doesn't *necessarily* matter how you get things done, long as they get done. Vital prerequisites are another matter though, no use doing a subject without its prerequisite if it heavily relies on that.
I was *technically* meant to do math in first year but i did it now (my 4th year). When they saw when i went in for something else, they were a little ticked off but there's nothing you can really do, especially if you plan to fulfil the requirement eventually. So, do what you like, long as you get things done eventually.