If you bought the car new, the representative might've mentioned about the x-year warranty in which it would cover for any electronics-based malfunctions, such as your navigation system or even the whole head unit itself. If you are out of warranty, yes, it would cost quite a few Benjamins to replace it. When I bought my vehicle, the representative pushed me towards getting the warranty AS THOUGH the electronics head unit goes out quite often after a few years of usage. Reading about your situation, I should've opted for the warranty myself.