Alrighty then... lots of fun. To save the next person some aggravation, here's what I ended up doing:
Take the time to properly understand the answer given... for a start.
Copy the truck, replace the GIUD with something generated, rename the truck file as well. Modify the .truck file...
In a .skin file,
I can use replaceTexture to replace one png with another.
What do I use to replace one wav file with another?
I can't find any reference to using a skin to replace a sound.
I know I can just replace a wav file with another, but I'm trying to do it right... as a proper skin...