If the fan on my air conditioning condenser isn't working, is there a chance it can be fixed?.?

I turned on the A/C central unit today (pretty old) and while I could hear the furnace working...the fan on the outside unit was not budging and there was absolutely no sound coming from it. My son who admittedly knows just a little about A/C said the compressor looks very old and maybe shot. So, is there any help or should I just start shopping around for a new unit? Also, if the A/C and the furnace are around the same age, 20 years? Do I need to buy everything new? I live in NY how much am I looking at?