I have this engine (and actually ran it for 3 hours last weekend) and have never had this issue. If you need to open it, there are 4 screws to do this (two in the back and I believe the others are under the lead truck . When you do that, only the top of the boiler comes off (there is a top and bottom of the shell), so when you take off the top of the boiler, the pipe will remain in place. When I have done this in the past, there were no issues with any of the under-boiler detail.
Just note, when you take it apart, be careful with the antennae leads as they are kinda fragile.