Taking the body off the loco was... interesting.
The "Driving wheel replacement" sheet shows that one of the screws under the cab is longer than the other, holding the keeper plate in place and fixing the chassis to the body. A diagram shows it in Red. Unfortunately, it shows the wrong screw! Since bodies are often a bit sticky to get off I did a lot of "gentle persuading" before I realised that there must still be something holding it and tried the other screw. It's OK, though, I think there is no permanent damage other than a few scratches that will not be seen.
Just as @Nile said, a bunch of wires on top:
Here are the wires under the footplate. The white wire might be affecting the fit but it's very thin.
More to follow...