It's not hard, but a little tricky. Do NOT try to pry loose the bonnets by pressing on the tabs under the chassis behind the buffer ends. You must remove the motor block first. There is an identical slot at each end of the motor block. There is a tab on each end of the chassis that clips into the slots. One of the tabs has a flat top and the other has a beveled top. You insert a flat blade screwdriver between the motor block and the beveled tab and pry it gently away from the motor block while pulling the block away from the chassis at that end. Once the motor block has cleared the beveled tab, it will slide out from under the flat top tab. There is a thin brass tube that projects up from the motor block through the chassis into the center cab section. be careful not to bend it as you remove the motor block. You will then see two Phillips head screws which hold the center cab in place. As the center cab comes loose the two bonnets will come free as well as the two flat metal weights that are held against the chassis by the center cab. The bonnets are held in place by a tab between the chassis and the cab in the center and a tab through the chassis at the ends. The roof is removed by pushing the plastic light "tubes" out from inside the cab. At this point, you can remove the air tanks, steps and wheel bearing covers if needed.
It's a nice little engine, although somewhat noisy until the mechanism wears in. There is room for batteries, R/C and a sound card in the cab, but you would probably need to put a "sugar cube" speaker under one of the bonnets. It might be possible to stuff the electronics under the chassis if you want to detail the cab.
Enjoy your new engine!
