1991 Mercedes Benz 300te Heat from vents when heater not on

I recently had to take my car into a mechanic for engine overheating issues. They replaced the fan, thermostat and temp sensor but now I feel a great deal of heat through the vents but my A/C system is off. My key is very hot as well when I took it out of the ignition. It may also help to know that my A/C system is not working (no cold air at all when on any setting) I need to find out what is wrong quickly. Don't need more issues. thanks