Sounds like your out of refrigerant. What refrigerant is it? If it is R-12, you''ll have a problem (in the U.S.) getting hold of it for recharging. If it is R-134a, you won''t have any problems, as it is available at any auto parts store.
I had a 1984 R-12 system that was empty. I pulled a vacuum and installed Enviro-Safe with great success. It is enviromentally friendly, available, and works great. There are other products, like Hot Shot out there, so you are not out of business.
First, determine which refrigerant and how much it uses and if it has any ports for recharging. Then, go to an auto parts store and buy yourself a manifold gauge set to fit it. Get your hands on some refrigerant and set to recharging.
It is not that difficult. Getting intimate with your system now will provide you with less frustration and more cold drinks down the road.