Obviously you should always be careful when working on your car, and ideally recognize when a job may, in fact, be too big for you. Some people have no business changing a wheel, and others are rebuilding engines and transmissions in their garage.
The problem is all these "void your warranty" posts. I've seen it quite a bit in my month on this forum and it's sort of a knee-jerk reaction by some people. Modding your car or working on it yourself will not void your warranty. In fact, there is no such thing as a wholesale voiding of your warranty. As was previously mentioned, you may have a warranty claim denied if something you did caused the issue, but Ford cannot and will not simply suspend the warranty on your vehicle. People need to stop peeing their pants about this.