I can relate, once I heard Tsunami sound in a loco, the rest was history.
I had the DCC sound bug and was seriously bitten!
Soundtraxx made a plug-and-play DSD sound decoder kit,
that requires swapping the PC board in the tender, and adding a speaker,
which is a relatively simple DCC install.
It's not Tsunami 16-bit sound quality,
however you might be able to pick one up on eBay.
You could probably fit a TSU-750 light logging decoder and speaker in the space,
after removing the original PC board.
But you will have to also install a resistor in one of the headlight leads,
to avoid overloading the LED headlight.
Because I don't have a ton of trains on my small pike,
I opted to sell my non-sound Shay,
and use another as a parts supply, for the two sound-equipped critters I have.
One is a recent Bachmann factory sound job,
and the other was bought from Soundtraxx several years ago,
when they were selling proprietary sound-equipped Shays, Climaxes and 2-8-0s.
Of course, once the Bachmann factory sound became available,
that became no big deal!
Lots of knowledgable folks here on the Freerails Forum, are here to help.