Not sure how easy this will be to do but disconnect the wires at the pump and protect them from arcing/ hitting anything. Then turn on the breaker and see if it still trips, if so then you know it's the wire and not the pump.

Doesn't fermenting poo create methane gas?

I can see the youtube video in my mind already.

THanks for all the helpful replies.

I downed a couple strong ales to increase my courage before attempting to remove the septic tank's hatch so I could pull the pump. Once the seal was breached, I was overwhelmed with feelings of sick and I aborted the mission abruptly. I decided that this was a convenient place and time to draw the line on DIY. I'm waiting for my buddy to come by and assist (aka fix it for me) as he's seemingly impervious so most disgusting things. Pending those results, I might be calling a pro and writing a check to make this problem go away.
Thanks again.

This made me laugh.