Quick math problem. Reward included.

[mused01]

I just recently enrolled in a math class for college and it's been a year since I took any type of math since I basically finished calculus in highschool and forgot almost everything in that class. Well, apparantely this class jumps right into multivariable calculus and expects you to know single variable calculus like the back of your hand. Needless to say I'm pretty screwed.

Anyways, the first person to solve this problem correctly while giving me a clean step by step manner will get $20 shipped to pokerstars immediately. Is this cheating? Eh, sure, but theres tons of problems like this and I'm just asking for a basic overview of how to do one. Anyways the problem is:

Compute dy/dx if y = cos(3x)e^(-x^2).

I know vaguely I have to use some kind of chain rule here as well as some funny business with e where it's basically repeates itself but honestly I'm completely lost.