Does your car make any noises when you turn on the A/C? I would suspect if you went right from Great A/C to nothing it's your compressor. Try getting under the car and turning the compressor wheel with your hand after you loosen the belt. If it doesn't turn freely then it is seized and you need a new one. Also check your belts. Some cars have 1 serpentine belt that runs the whole car. Others have a second belt that drive things like A/C and power steering. If the compressor is seized and you don't have the cash to get a new one (they can be expensive for parts alone and it is a good idea to have a mechanic install them because of the refrigerant in the A/C system) you can get a dummy wheel that can be put in place of the compressor that won't do anything but keep the belt tight. It is important to make sure the compressor isn't seized because if it is and you drive around like that it will shred your serpentine belt. You can also try to get a bypass belt that is shorter and will run around all the parts other than the A/C until you can fix it.
Other than that make sure your belts are good, your coolant is charged and you haven't blown any fuses. Also this section is more for computer hardware, but I'm sure with a few modifications we could turn your Caddy into a mechanical analytical engine. I know I would brag if my computer could do 100 mph and weighed over a ton.
Those whom God loves, he must make beautiful, and a beautiful character must, in some way, suffer.
-Tailsteak author of the Webcomics 1/0 and Leftover Soup