I'm a software engineer, but I majored in Neuroscience in college. I loved it!
I'll try to answer each one of your questions:
Are there many job opportunities in neuroscience?
If you're really into the science behind neuroscience and want to possibly make groundbreaking discoveries in the field, you can pursue neuroscience research. This would involved going to graduate school, publishing research, getting a Ph.D., and maybe even starting a lab or being a professor.
If instead you're really into using your knowledge or expertise in neuroscience to help humans in a medical capacity, you can become a neurologist or neurosurgeon. A neurologist specializes in medical conditions relating to the brain or nervous system (e.g. Alzheimer's disease, Parkinson's disease, etc.). A neurosurgeon performs surgeries specifically on the brain or nervous system. Both these jobs require you to complete medical school (4 years), then an internship/residency afterwards that can vary in length.
Also, just because you major in neuroscience doesn't mean that you have to do something neuroscience related as a job. You learn a lot of biological/anatomical/physiological concepts that provide background knowledge for a lot of biological or health-related fields. Also, a lot of neuroscience majors take courses in related fields such as psychology or cognitive science, which have more of a sociological or anthropological angle.
Is there a lot of room for growth in the field of neuroscience?
Definitely! Since there is so much about the brain that is unknown or undiscovered, the possibilities are endless. New discoveries are being made and new technologies are being invented all the time.
If you majored in neuroscience, are you happy with your choice of major?
I'm definitely happy that I majored in Neuroscience. I was (and still am) fascinated by the brain, and majoring in Neuroscience was a chance for me to not only learn the intricate details and secrets of the most complex organ in existence but also to gawk at the sheer potential for new discovery. I highly recommend it!