I'd recommend getting a tutor now. Get some algebra review, and get support so that you do really well in trig.
Trig is stuff that your premed competitors had in high school, and given that you view math as difficult, I'm thinking you've got yourself psyched out. Set yourself up to succeed, to comprehend, and to use this math class to learn study skills. There's some memorization, and then you have to understand the concepts and apply them to problems. Later on, in physics, you'll need to have a conceptual understanding of why a trig curve describes the motion of a spring (for one example among a boatload of 'em). If you struggle through trig, you'll have a really hard time in physics, is my point.
To answer your question, here are a few things you should be really comfortable with on your way into trig.
1. Concepts like integer, fraction, negative/zero/positive, exponent, coefficient, greater than, less than.
2. The concept of a function, such as multiplication or a square root, where you should have a sense of what the result of the function is as you progress along the integers. So if the function is "5 times X" you should be unintimidated by thinking about what the result is when X is zero, negative 4, 157, 10**8. X gets bigger, the result gets bigger. X gets smaller, the result gets smaller.
3. Basic graph concepts, like x intercept, slope, and how to make a graph of a function that looks like ax + y = z. You should know roughly what simple functions graph as a line, and what simple functions graph as a curve.
In trig you'll use these concepts from day one. And after trig, you should be capable of drawing the sine and cosine curves upon being rudely awakened at 3 am with a flashlight in your face.
Go get 'em. Best of luck to you.