I passed my certification exam!!

There are medical, healthcare and nursing informatics courses for credit and adult education (without credit) courses out there.

That all depends on what you mean by "cost tons of money. Try doing an Internet search for: "Nursing Informatics courses"

It also depends on exactly what it is you are seeking to learn about - computer basics, the fundamentals of nursing informatics, system life cycle, change management, what?

I'd suggest you do your research and start by reading nursing informatics (NI) books that can provide you with the basic and fundamental concepts of the specialty. Do a search on Amazon.com using the terms "Nursing Informatics" and "Healthcare Informatics" Search this forum and you'll also find several recommended NI texts.
Related to being a supper user at your organization you will find that the priority will be becoming an expert user of the system, being involved in the implementation process by perhaps being able to teach the system to others (train the trainer methodology) and or being able to trouble shoot simple system problems and communciate system issues to IT/IS. These priorities are far different than learning and mastering informatics concepts and principles.
Good Luck