2004 Chevrolet Cavalier - HVAC issues

My car is clicking when I turn on the air conditioning, plus fumes are coming in when I.turn it on. Smells like oil or maybe leak in Freon. Not sure but hope you can tell me

Multiple problems. The clicking is blend doors. The smell most likely is the heater core, or could be the evaporator coil.
Only a qualified auto AC shop can tell you for sure.