Plug-n-Play decoder, non-Plug-n-Play Loco?

[P5se Camelback]

I have acquired a non-Plug-n-Play ALCO Models brass Alco S-2 which I intend to paint as a Reading S-2 in service for a number of years. I bought it because it was relatively inexpensive (cheaper than a current plastic offering of an Alco S-2,) and it seemed to me that a diesel would be a good first decoder install (get my feet wet prior to jumping in the deep end with the remotoring and installing a decoder in an older brass steam engine.)

Then I discovered that the proper Soundtraxx decoder for an S-2 (Alco 539 Turbocharged) is the TSU AT1000 Plug-n-Play for an ATLAS model of an S-2. I'm sure the decoder would work in this application, but I have a few concerns ...

The decoder is a "Plug-n-Play" style decoder, no wires, no shrink-wrap cover. The Atlas model has a non-conducting plastic shell, I have a brass shell -- very conductive! The decoder is set up (apparently) for plugs of some kind and I will most likely be using the typical color-coded wires.

I am asking for a little kind advice here and maybe even a recommendation for a speaker for in this little gem of a switcher (I haven't had a diesel model since the Varney F3 I put a single power conversion truck under in 1958!)

When I'm done with the install, and have done some magic by coating it with a few layers and dustings of atomized pigment, I will carry it with me when I visit the local (some 35+ miles away) model railraod club, a Digitrax controlled multi-level layout in its own dedicated building.

But I am seeking a little advice before I screw anything up!