Going back to school for another degree

So reddit, I have an undergraduate degree in Psychology, I graduated in the spring of 2010. During my senior year I worked in a neuropsych lab and loved it. I got to go to conferences, and actually do some actual science. However I had a pretty strict line of classes I had to take to graduate (poor planning) and so I never got to do anything other then the basic neuropsych course offered. Also my GPA was nothing stellar, sitting just under a 3.0 (I'm a little ashamed of it, I could of done better easily).

Shortly after graduating I got a job at a major university working in a vocational program with Autistic Adults. Now comes the part where I could use some advice.

I love my job, and am in no hurry to move onto something else. That being said I don't want to do it forever, my real dream being to go back to graduate school for Neuropsych. I get to take free classes through the school, and can go anywhere in state. There is a high concentration of very good schools nearby, so I can take pretty much anything I could ever want. It should also be said that I loved going to college, though not really for the same reasons as everybody. I genuinely love going to class and learning things.

I have a supportive family, and no debt. Should I take classes on the side to try and line up a second major (my credits from my first undergraduate program will transfer)? Should I work for a few more years and then try to go back to school full time? Should I just try applying for masters and PhD programs? I could apply for lab positions at the university to get more experience, but would that be worth leaving my very enjoyable job that I have right now?

I am sorry for any spelling or formatting issues, I am not an experienced poster.