Is there anyway to edit the model of a train like up sd70m I want to correct some things but don't know how I heard you can by editing the gepcdx file but I don't even know how to open it
Sounds like you should read this thread https://forums.dovetailgames.com/threads/you-can-edit-the-3d-model.82109/
You cannot edit the exported models without having the source files (which you cannot get). You can only change child objects attached to the mesh.