Its easy to change the disc brakes and rotors on most cars. Here's a disc brake replacement video we made on GardenFork.TV . Use this video as a initial introduction on how to repair the disc brakes. Consult your car's repair manual for the exact procedure for your vehicle. Be sure to jack up your car on the frame and to use jackstands. Chock the rear wheels to keep the car from moving while you are working on it, work on flat surface, and set the parking brake. Also be careful of brake dust, as its not healthy to breathe.
Be sure to buy disc brake grease and some spray brake cleaner, it gets messy with all the dirt under the wheel wells. We wear latex or nitrile gloves to keep our hands clean, the nitrile gloves work best. And you get what you pay for when buying disc brake pads, don't cheap out, these things stop the car, you know. Work on one wheel at a time, that way you can look at the other wheel as a reference.
We also have a front wheel bearing replacement video that show how to remove the brake caliper and how to install new wheel bearings.