Oh boy, here we go again - another "cute" N scale switcher (sigh)... OK, let's get on with it...
The chassis is all metal (and relatively hefty). The motor is an extremely small open-sided deal (and presumably a 3-poler). All gearing is plastic. All six wheels are geared, but only the outer four actually provide pickup. There are no traction tires. A non-directional headlight is mounted to the front of the chassis. The Rapido-style couplers are also chassis-mounted.
Big surprise, this model isn't much of a runner. The wheel flanges are ridiculously huge, making even Code-80 turnouts a hazard (and you can flat out forget about Code-55 entirely - turnouts or otherwise). And why "they" (Atlas or Roco) decided to make this thing an 0-4-0 in terms of pickup is beyond me. As is, it's a total stall machine. Yeah, once again, what we have here is a loco that will run around a simple circle of track more or less reliably, and that's about it.
Circa 1982, Atlas discontinued this model along with the rest of their line of Roco-made locomotives (coinciding with their new partnership with Kato).
To remove the shell, simply unscrew the big ugly screw on top of the shell. It should lift right off at that point.