Not meaning to be a smartass [Well, smartass, yes; hostile no :-)], but remember the M2 is simple enough that two generations of GIs had no trouble with it...
Take the metal stuff out of the wooden thingie, and slowly cycle the operating rod, and cycle the selector back and forth a few times. It oughta all be pretty obvious, since it'll only go together one way...
You can find the GI Manual at a lot of gun shows, in Paladin Press catalogues, etc.
Regardless of the effectiveness of their ".32-20" style cartridge, they're fun little chatterguns to shoot. And the stock won't break if you have to butt-stroke somebody, not like some Mattel Models I've seen. :-)