To begin with, you need to find a new windshield shop. There is no need to remove the wiper to replace the windshield. They only need to use a thin piece of plastic between the windshield and the wiper unit to slide the windshield into place, sort of like using a shoe horn. Your shop obviously knows nothing about these cars.

Now, to the a/c. Is the compressor clutch turning and the fan motor blowing? If both of them are okay, then the problem is not a fuse.

With the engine running and the a/c on max cold and max fan speed, if the clutch is not engaging, the problem is a leak in the system which has lost refrigerant. If the clutch is turning, look at the sight glass on the filter drier just behind the drivers side headlight. It should be clear, if there are bubbles, then again there is a leak.

Good news is that your car is an original r134 system, so refrigerant is cheap. You can simply go to an auto a/c shop and have it recharged. If you want to do this yourself, you will need gauges at a minimum, and if you have to repair a leak you will need a vacuum pump. Also, this is a job that deserves lots of knowledge. If you don't know what you're doing you can cause personal injury or death.

Good luck,