I have a DC "HO" GP38-2 Diesel loco. What DCC decoder do I need and where can I purchase it?
What type of decoder do you want? Lights and direction only or full blown with sound and all the bells and whistles.
Check out the decoder suppliers websites and check their application charts.
I buy from Lichfield Station for some years. Sound and non sound decoders.
http://www.soundtraxx.com/
Hope you understand the basics for DCC or it will be quite a challenge. It will not be plug and play.
You did not mention the brand or age of the loco.
No idea of what your expectations are.
Rich