Need help getting older Big Hauler 90-0100-27 engine running

[Chasp]

I got the Bachmann's Big Hauler #90-0100-27 out of the attic for the first time in 20 years. Hoping to surprise the grandson with this running under the Christmas tree. Luckily when I last put it away I took the batteries out of it. But with new batteries installed the engine will not run. The RC control lights up but no power to the engine. All switches are on.
There was a little oil (or it seemed like oil) coming from the motor compartment. The bottom of the case was damp with it.
Any ideas where I can start to make this run again?
Any help will be appreciated.
Thanks

[Ken G Price]

Did you post this to the Bachmann large scale forum?
That would be the place for it.

[Chasp]

Thanks, I'm new to this.