Having a bad day: Speedo problem, then Idle problem

[boxstershorts]

The day started when I wanted to finally fix the speedo (wife went shopping and I was home alone). I had replaced the gauge face but mispositioned the needle. Anyhow, when attempting to remove and replace the needle (just as gently as I did it the first time) the little plastic shaft that the needle plugs onto must have come dislodged from the inner mechanism because the needle no longer responds at all. Am I doomed to buy a new cluster? I decided to explore the speedo and I got down to the little white plastic module that controls the needle...can I buy this part somewhere? I actually relatively easy to get down to that point (I don't recommend playing around on it unless you're speedo is already toast and there is nothing more to lose as in my case).

So, in my depression over the speedo, I figured I'd do my easy fix and change the tail fog light that was burned out. Turns out it's not the light (nor one of the 3 tail fog light fuses (???)). So I zero in the gray and white wire as the culprit. I decided to follow it and see if there was a cut in the wire along the trunk firewall where all of the wires are. I got to a black connector (one of 4 similar ones) but this was the easiest access connector where I can see the gray and white wire. I disconnect it to clean and measure resistance. To check the voltage, I had to turn the key but I turned on the engine (SHOULDN'T HAVE DONE THAT!!!!!) the check engine came on and I turned the car off immediately. I never fixed the wire problem and now the car is idling at 2400rpm!!! What did I do?!?
Did I blow a component or is the onboard computer overcompensation for whatever it is interpreting the problem as?

Having a bad day. (and now looking for something else to do in my spare time alone when the wife is gone shopping!).

JP