Engine
Before starting any serious disassembly work, especially something as complicated as a model steam engine, it is a good idea to take a photo of the unit. This photo shows the drive mechanism. This is definitely the most difficult part to put back together later on.



First step is to disconnect the tender from the locomotive. It pops loose from the engine, or, the other way to do this, unscrew the lead truck of the tender, and the drawbar assembly comes loose.



The cab can be removed by gently prying the sides of the cab out a bit and moving it up. It will pop off. Grab the back or the front of the boiler and lift it up (lifting from the front shown in the photo below).



Remove the boiler.



Pry away the side "flares"/walkboards which are held in place with two pins. The weight can be removed and the lightboard can be slid out of its spot. There are screws that hold the two frame halves together. I have not had to go that far with this engine, so that is not shown.



Tender
The main body slides off the frame just by pulling it up. You may need to pry the side out ever so slightly.



The black plastic piece (second from the top in the next photo) snaps in place, so you will need to ever so slightly move the frame sides out a bit and insert a small screwdriver to lift it from the bottom. After that, all the remaining parts fall out. The contact strips touch the brass pickups in the trucks to provide extra rail pick-up points.