questions about bad AC /evaporator

After reading Ashman's post about his leaking evaporator/dying AC, I got a little concern. It seems that I may have a leaking evaporator because I noticed the same symptoms that Ashman described. Although I only found a few drops of greenish oil near the tranny and the leak has never reoccured (I have checked under the car occassionally and no longer see any leaks since first discovering it), the AC no longer blows cold air. Well, I'm not too concerned about having no AC--I can live with that for now. My concern seems to be about adding oil to the evaporator or something like that so that the compressor won't wear itself out. (Someone said this in reply to Ashman's post.) What does that mean? First, I don't even know where to add the "green oil." I don't plan to use my AC, so is adding oil necessary? Does NOT OPERATING the AC mean there will be no moving parts in the AC unit, and therefore no oil consumption? I don't plan to fix my AC unit/evaporator or add freon anytime soon. Is operating my car (90 190E) with a leaking evaporator or a faulty AC bad for the engine? I know these are paranoid questions, but I just need to know that everything is alright. Thanks.