Getting in PA school with a career change?

I am beginning to think about the possibility of PA school but I am not sure how to accomplish this or if it is possible. I am 23 years old and I have graduated with a BS in biology in 2018. Since graduating I have been working as an associate scientist at a cosmetics company. Therefore, I have about 1.5 years in research experience out of school but no medical experience. My GPA in undergrad is 3.17 (which is low and probably will hinder my application). I have also taken the GRE- 300 score and 4.5 writing score. How can I begin to gain the medical experience that I am lacking, am I too old to start thinking about this career change, and what pre-reqs are needed for PA school? Also, does being a PA in a top program vs. middle tier program have impacts later when graduating?