1997 Ford Escort Wgn AC now doesn't work?

Had a new engine and trans put in a few months ago and I think the AC worked when the mechanic brought it back to me - his wife and I drove it around for awhile but don't remember if we ever used the AC - yesterday I tried to use the AC and only hot air comes out no matter where I put the switches. Any ideas on where to see if it has freon or needs coolant? If a fuse went bad would it work at all? Or something else?
I don't drive it much so the last time I drove it only needed to use the heat. (have two cars)

The only real way to tell the condition of the refrigerant is to throw some gauges on it. You can check the fuses to, but low refrigerant would be the most likely scenario