Ok, so I'm a car moron, so I have no idea whats wrong here. When going really fast, like highway speeds, when I hit the brakes, the car vibrates some...almost seems like the brakes are warped somehow. And also, those clowns at Jiffy Lube told me that my brake fluid is low, and that means I have a brake problem.

Can I get some help? Any ideas what this is?

Vibrations is probably warped rotors.

Low brake fluid could mean
1) a leak somewhere.
2) brake pads are worn out allowing the fluid to travel further down into the caliper.

Suggestion: Take the car to a qualified mechanic or to a Nissan dealer. Jiffy Lube does NOT qualify in my book.

Vibration while braking is warped rotors. There is a TSB on it (see the TSB sticky thread). Take your car to your dealer and have them check out the brakes... mention the fluid too.