As long as you show up for every class, do your assignments, and study then you will be fine. Actually I found the science classes to be the most interesting part of my pre req education. I loved learning how the body was put together and worked. It's truly amazing!
A lot of this sort of learning is simple memorization so find a system that works for you. Personally I used the flash card system -- I'd right the question on one side and the answer on the other. And I would just go over and over it till I had it down.
My hubby did it, in his mid 40's, and he was a non science type - his first degree is in history. He was top in his class, because he was interested, committed, and he has a support of wife (me) to listen to him complain about nursing care plans
! But I am getting a head of myself. Just worry about the pre reqs first Tony. I think you will be pleasantly surprised how well you will do once you are in class. Remember they break it down to bite sizes pieces, you won't have to know it all in one class.