With more than 30 minutes to dedicate to the Impala, I was hoping to make some progress today. I got there and had the fuel pump out of the tank within 10 minutes. Here's the nifty little trap door that those geniuses at Chevy thought of that kept me from having to drop the tank.
Once I had the pump in my hand, I was able to determine which wire was hot and which was ground. Then I hooked up to jumper wires to the Subaru and, even then, the pump did nothing but wreak of gas. So then my next move was to go to the parts store and pay $270 for a new one. I brought it back and hit it with 12 volts and it hummed so I knew I was home free. Before I threw it back in the tank I had to splice in a new connector as Chevy decided the old one wasn't safe enough. The new pump was a bit finicky about getting all situated but it finally went in. I primed the fuel system, hooked up jumpers off the Subaru and the car fired right up. It idled while I buttoned back up the interior and then I drove it around for 30 minutes to charge the battery back up. Everything was cool and I was so glad that it did turn out to be the pump.
Unfortunately, the radio went into "locked" mode as a result of the dead battery. After a bit of research, I found out that only the dealer could turn this back on. Those bastards get a $100 to do that and it requires a scanner to. That is the dumbest thing I think I've seen in a while.