Shell Tank&Diesel Horn #46208-Need Circuit Diagram

[Sunshine Express]

My Bachmann Shell Fuel Tank and Diesel Horn Model3 46208 has been working well for many years.The kids love it.
However shifting it a little,during painting alongside , one wire came adrift from the circuit board,and when trying to re-solder it ,two more came off. A short circuit resulted when trying to reconnect.   I am not a new age electrical wizard  at 85 years,but would like to get a circuit diagram to take to my electrician fellow modeller to do the repairs. Any help appreciated.
Owen Robinson