Forget the previous message I posted on March 18th, 2021.  I've located my owners manual and it provided me information locating and gaining access/removal of the factory decoder. 
After additional research and communicating with SoundTraxx I now have a plan that should get me sound.

To start, I don't have DCC.  I operate my trains with a Tech3 Command Power Model #9500 controller made by MRC. 
My Spectrum 2-6-0 Model #81496 train doesn't have sound (I think).  I have 2 plugs coming out of the rear of my Loco, a 2 pin and a 4 pin. There are 2 receptacles on the Tender to connect both plugs.  I can run the train with the plugs connected and not connected to the Tender and there is no operational difference. 
I removed the top of the Tender and found there is no speaker.  There is a place to mount a 3" speaker on the bottom floor of the Tender and there are 2 wires, one is gray connected to left wheels and the other is black connected to the right wheels.  Both wires are connected to the 2 receptacles.  Does this mean I have sound capabilities in the Loco and can't hear it because I don't have a speaker in the Tender?  If I add a speaker to the Tender and connect the Loco plugs to the receptacles on the Tender would I possibly get sound? 
It looks like the 2 plugs are wired to the Loco motor.  I tried to disassemble the Loco to see where the 2 plugs go, but couldn't find a way to do so. I couldn't find instructions on how to disassemble the Loco online, and there are no assembly/disassembly instructions in the operating book that came with the Loco.  Where can I find additional instructions?