My previous post hasn't been approved by a mod yet, but here's an update.
That connector is the right one. I don't want to spend $50 on the 14-pin adapter if I can make this work without one. The tape adapter is also something I want to avoid using because they don't seem to be as reliable as they should be.
I looked at the "Need help identifying..." thread and found schematics for a similar radio. The pinouts matched with my radio's labeling on the PCB. Even with that knowledge, I was unable to activate the cd/aux input mode. I'm guessing those aux converters have some sort of digital signal to send to the radio unit.
I tried riding into the radio's input signal again. This time, I had a solid electrical connection. I was still able to hear the static or station playing in the background. The only way I can make that work is if I transmit my own FM signal to prevent local stations from interfering with my music. That involves spending more money, though.
The last thing I see that I can try that doesn't involve adding components to this is the NAV inputs on those schematics. I'm guessing those are inputs for a GPS system, but my radio might not support them because it is a different model.
Edit: My dad found a FM cell phone sound transmitter thingy. He said it didn't work well, so I "extended" the antenna directly to my radio antenna input. It works, but I wish I could have done it directly through the radio.