I had a new radio/cd player installed at Circuit City this past Friday, now my air conditioning fan only works on 4 - it was working fine when I dropped of the X. Did they screw up my electrical?

Most likely they unplugged and forgot to pulg back in your resistor. This controls the different fan speeds. Without a resistor it is always on high. Either that or it is just a coincidence that it went bad at that time. Either way it should be easy to hook back up or cheap to replace. It is located behind the glove bov somewhere on the evaporator ventilation box.