Glenn,
A year or so ago there was an article in Model Railroader about an install of a SoundTrax decoder and speaker in the tender of the 2-8-0. I don't know where that issue is and I am leaving in about 10 hours for Disney World but maybe someone else can tell you. You might be able to find it on line or possibly at a library if the have they subscription to the magazine.
It looked like a prety straight forward install.
Let us know if you decide to do it.