my ac compressor is bad is it hard to change out 92 cad deville?

Just because the service A/C light is on, this does not mean that the compressor is bad. Unless you have more information than you are revealing to us, it could be telling you that the system is low and need to be inspected and serviced. If you don't know what your looking at, get some help from someone that does know or take it to a professional. A/C is not a field for the novice, you could do more damage than good and or hurt your self. Pressures can get as high as 450 psi and things tend to come apart at those pressures. Do the smart thing and play it safe.

its not hard to unbolt and install a different 1 but...... to get it to work right requires you evacuate the system with a vacuum pump. then to charge it with r134a. if your mechanically inclined switch it out then take it to a shop to finish it up