The other weird thing is that I had an airbag error light turn on, but not until AFTER I swapped the doors!
After a little work (and input from folks on forums) I was able to discover the issue was because of a sensor on the "Seat Belt Pretensioner", which is a device attached to the seat.
The new driver seat for the car was pulled from the parts car, and THAT car had been in a collision. So, the new seat was telling the car the wrong thing!
I was able to swap the pretensioner from the one seat to the other. It was pretty easy to do, other than it meant pulling the driver seat out of the car one more time!
Once everything was plugged back in, the error was cleared!
I've now taken the car in for emissions testing and that was the last thing I needed for full and clear title/license/registration/etc. to legally be on the road.
The car drives well, and my wife likes the stereo.
Here's the part that I had to replace to fix the Airbag error.
Here are the most recent photos of the exterior of the car.
Those two photos aren't great, as they were taken first thing in the morning, and there's condensation on the car. The roof of the car is SIGNIFICANTLY better looking than it was before. I'm pretty happy with how I improved that. The rear fender still isn't perfect, but a far cry better than what I started with.
I still need some touch-up paint in a few spots. I'll probably try a little bondo too sometime, but when the weather is better for it.
Still to do: Getting the seats and door interior panels all to match.
Future Project: Add a 120/240VAC Power Inverter to run from the car and power my house in a blackout.