Need help on converting to DCC unit is NIB
Not a good choice for your first conversion, or even your second. Start with something simipler and cheaper like a non-DCC ready Bachmann Plus or Spectrum diesel. Which would be not too different. An Athearn diesel is too different.
I tried to find any info on a PSC Shay and I came up with a little more than nothing. It might take some time before someone with experience installing a decoder with that particular model.
I wish I could help you, but I don’t know how mechanically inclined you are or how much experience you have with installing decoders. It would be difficult to guide you in the installation process without being there in person or without any exploded view diagram. If you don’t think you can do it yourself, have it installed. I’m sure you laid out a good amount of dough for this model and paying just a small percentage of the cost of installing a decoder is well worth it.
Tony’s Train Excange is one such vendor. Perhaps other folks here in Forums will recommend some installers who they have used and were pleased.
If you still want to attempt to install a decoder youself, here’s a link to some general instructions. Decoder basics. Selecting the right decoder is important by Keith Gutierrez and Lee Rayburn