Misfire + black spark plugs on one side

My 95 Z28 started sputtering/misfiring and idling rough yesterday. Also started what I believe fuel in the exhaust like I'm running rich. Pulled the plugs on the drivers side and they're all black. Got 2 off the passenger's side before I called it quits for the day, and those 2 are gray and looking good.
I've done a bunch of searching, haven't found a post with the same findings with regard to the plugs. Running rich seems most commonly caused by exhaust leaks before the o2 sensors. My father doesn't think its that - says it would have to be pretty big. Another common cause seems to be loss of vacuum pressure to the fuel pressure regulator. But, all the plugs would be black then right?
I'm hoping that it's a bad o2 sensor. How would I check that? I don't have scanning software.
What would cause black plugs on one side?
Also, preliminary inspection of the wires is that they seem alright. Thanks in advance for any input.

The question is, which came first.... the misfire or the black plugs? A misfire will cause that bank of the engine to run rich. So will a faulty O2 sensor or wire on that side. And an exhaust leak doesn't have to be very big. The fast moving exhaust gasses in the primaries will "educt" air into the exhaust stream. It takes very little air in the exhaust to screw up the O2 sensor readings.

Swap the O2 sensors side to side, and see if the problem follows the sensor. That would confirm a faulty sensor.

Might be time to pick up the scan software and a cable, and start learning how to read the data.

Thank you very much Injuneer.