A cosmetic dent that doesn't go through the skin, you can leave alone - it's not going to get worse on its own. But once a panel is cracked or the foam core is exposed, swapping it yourself means matching a specific builder-era model correctly, which isn't a hardware-store part. Order the wrong panel and you're stuck with a color or profile mismatch that's now yours to explain every time someone pulls into the driveway.
The other risk is the door's balance. Panels on an insulated door aren't just cosmetic skin - they carry real weight, and installing one wrong changes how the springs and opener handle the door afterward. We'd rather you call and ask than end up dealing with a door that won't stay in track.