1991 Passat Stereo Removal and Installation

Hi, I just bought a Passat and the guy that sold me the car told me that I had to install the stereo. The stereo is just sitting on the panel, but I have no idea on how to take it out. Please, if anyone knows let me know.
Also I have a problem with the wiper blades and the windshield washer pump, they activate by themselves all of sudden and my whole system restarts (clock, trip odometer, lights blinking, etc.) if anyone knows how to repair it, please let me know. It'll be very much appreciated.