Hi Greg and Happy New year ,
My speaker was powdering also. I buy a lot from Patrick’s Trains in Wheeling West Virginia. He is awesome to deal with so I kind of respected that and like to give him my business!
He did however try to lead me to buying thru MTH but after talking with him he let me speak with his technician and ordered the speaker and some other things from him.
When I replaced it I cut the wires as close to speaker as possible. Had to be real careful stripping the wires! They are so small! Made sure positive to positive and negative to negative and then soldered them. Put it on the track and everything ended up perfect!
Good luck and I’m sure once you replace it all will be fine.