I have a 98 Cavalier & just replaced my plugs wires & air filter because the car was stalling. After doing this the problem continued so I purchased an OBD2 to test. I get the code P0452 which is Evaporative Emission Control System Pressure Sensor Low Input. What is this & how do I get it fixed?

That DTC indicates a problem with the fuel tank pressure sensor or circuit.
The sensor monitors vacuum inside the fuel tank during Evap operation.
Diagnostics on Evap systems are extensive and require a digital voltmeter and a scan tool that is up to date.
The fault could be the tank pressure sensor, the vehicles PCM, or wiring harness concerns.
That code may also be erroneous, and should not be responsible for the vehicle stalling.
Further diagnosis is necessary.