My aunt is a professional photographer and I was showing her my FZ1, she was very impressed! I told her that it was F2.8 through the entire zoom and she didn't believe me. She said that for it to be 2.8 "the lens would cost thousands of dollars."

It's probably true in a professional dSLR camera since the lens is much bigger and heavier with more glass because of the larger sensor...

On your camera the CCD is tiny (hence a much smaller and less expensive lens) for the same effective f/2.8 and collects less light because of the smaller area -> How high in ISO can the FZ1 goes until the noise level overwhelm the image? :?

Well, after 200 it starts to pick up some noise. Here's some noise at f2.8 and 400 ISO:

That's where the difference is with larger sensor (and larger lens with the same aperture) you can achieve much higher ISO (@ a cost)!