There's a plastic pin above the trigger; push this through (I used a chopstick) and you'll be able to pull the entire action out of the rifle. There's three basic parts, the lever/trigger assembly, the slide, and a shuttle that rests on top of the slide; the pin on the shuttle goes in a slot that's connected to the lever.
Yes winchester did make a model 250 lever action rifle from 1963-1974.
Jim Green's Gunworks has a great pair of videos for assembly and dissassembly, on you tube. downeastgunworks.com
Use Google and search for '1917 Enfield rear sight'. There are a number of websites that can help you with disassembly, etc. Start with www.cruffler.com
No way to post pictures
The Gun Digest Book Firearms Assembly and Disassembly Part 5 Shotguns has an illustrated description of the model 97 disassembly.
It was made between 1934-1946. 100,030 made. No serial numbers. Your best bet is to find a copy of The Gun Digest Book of Firearms Assembly/Disassembly: Rimfire Rifles by J.B.Wood
Get a copy of the Gun Digest Asembly/Disassembly instructions for centerfire rifles. The Marlin Mod 36 is included.
A Sears Moels 300 is a Winchester Model 1400. For a manual, go here: http://www.stevespages.com/page7b.htm For disassembly instructions, get a copy of Gun Digest Assembly/Disassembly for shotguns. Aslo, gunpartscorp.com has an on-line exploded diagram for the model 1400.
Contact Marlin.
Why would you want to? Oh well, it's your gun and I hope this helps: http://www.rarewinchesters.com/images/Exploded%20Views/1866-73-dissassembly.shtml
www.savageparts.com has a schematic. I advise against disassembly unless you absolutely have to. sales@countrygunsmith.net
Call Beretta customer service.