Hi there! I am in my first semester of nursing school now and wanted to share my experience with you. First of all "hard" is so subjective! It totally depends on you! If hard means difficult to learn and retain the info, no. If hard means having to study and read more than I was used to then yes!
Already being a pharmacy tech will at least give you a huge advantage when it comes to phatmacology
The science pre-reqs were not as bad as I thought they would be, though they certainly required more time than my other college classes. My best suggestion is start small if you can. Take just an a&p class and nothing else that semester if you're really nervous about it. Test the waters if you will.
Luckily, we live in the great age of information and anything you have trouble with you can get more help online.
If you are diligent with your time managemnet and stay on top of your studies (don't try to cram!) Chances are you will succeed.
Good luck to you feel free to pm me with any other questions!