P0440 Diagnostic and Repair Guide for 2001 Chevrolet Express 1500 6Cyl 4.3L - Where to Find EVAP System Parts

I own a 2001 Chevrolet Express 1500 with a 6-cylinder, 4.3L engine and am currently experiencing a P044 T code (Evaporative Emission System Malfunction). The emissions technician is unavailable, and I'm having trouble locating a replacement canister or related parts at local auto stores. The vehicle occasionally emits a noticeable exhaust smell—especially during startup or when backing up. When the engine is running in park with the heater and blower on for any length of time, an overpowering, slightly burnt odor builds inside the cabin (I’ve even noticed it while driving with my disabled support animal sleeping after vomiting). The smell can be strong enough to make me feel dizzy. The P0440 code appears intermittently and clears after 5–10 ignition cycles. After that, the check engine light comes back on and stays illuminated. I recently replaced the camshaft position sensor (which previously triggered a separate DTC), and no further codes have appeared for that issue. I’ve read several posts about P0440 but haven’t found specific guidance tailored to my 2001 Chevrolet Express 1500. Could someone provide a clear, step-by-step breakdown of the EVAP emissions system—what it does, how it works—and where I can find replacement parts (like the fuel vapor canister, purge valve, or hoses) for this model? I’ve already replaced the spark plugs due to visible charred electrodes, but there’s no improvement in symptoms or DTCs. I also have a fuel filter on hand—does that play a role in P0440? Any advice on how to troubleshoot the EVAP system systematically would be greatly appreciated. Thank you for any help! - HB