I’ve had this LGB Forney for 20 years. I purchased it new from Eastside Trains in Kirkland, WA. It never, ever ran well. I brought it to Dave Goodson about 3 years ago and he took it apart and fiddled with it and got it running. And it ran well! However, after about a year it stopped running again. Dave was not able to help me again as his health was failing.
I watched him take it apart which as he explained because it was a newer model made in China there was a different trick getting it apart compared to other LGB Forneys. He said there are tabs on it not on the other Forneys that are delicate and needed to be watched out for when taking it apart.
After a ton of research today and with the help of ChatGPT I discovered the model of this Forney is a 25251. There is no number marking on the bottom of this loco. It appears there is no exploded view diagrams for this Chinese model. However, ChatGPT outlined step by step how to take the body off an access the internal wiring/circuitry which I will be removing the majority of. The plan is to convert to Blunami 4408, dead rail battery power. I did drop the motorblock today and confirmed that the motor does actually run when power was applied to it directly. So that is good. I don’t plan on keep the smoke unit operable as I rarely ever run with smoke. I am going to attempt at putting the Blunami and battery in the bunker and see if I can get a speaker in the boiler.
The fun starts tomorrow! 
I’ve traced all the wires and have ordered the Blunami 4408, battery and wire harness.