This is interesting to me. I don't have this or ever worked on it. The steam engines I have taken apart, were all straight forward with screws at the cab, and others at the front of the boiler. I think some of the larger articulated can be more complex. Some even have steam pipes that need to be disassembled the correct way.
I have both the 3rd Rail and the MTH versions and both come apart fairly easily. I always wanted the Lionel version in my collection and just ran out of space and money for anymore engines.
I bet Alex M has taken this apart!
Looks like the one that Hot Water also had!