I have a 96 with 160k on it and have never had a problem with the AC.
I can tell you that there is a low refrigerant cut out switch that keeps the compressor from running if it senses that there isn't enough refrigerant (r134). Check to see if the clutch engages, you can by pass the switch. it's usually on top of the accumulator just jump accross the two terminals on the plug that hooks up to the accumulator, if the compressor runs..you are most likely low on R134 and may be able to recharge it yourself...
It did leak from somewhere but unlike your refrigerator the sealed system in an autommobile is not all metal to metal. (o-rings in/on hoses etc.) and some leaking on an auto system can and does occur without serious leak problem...o-rings dry out, shrink during the winter etc.
It's hard to know on the recharging how much gas is gone but you are usually safe to ad a 12 oz. can