See the link below. This will take you to the schematic for an RG 14 at the Numrich gun parts corp website.
You can find it on e-gunparts.com
Egunparts has some.
Take it to a gunsmith and ask for help
http://www.e-gunparts.com/product.asp?chrProductSKU=PDF0546
Go to Numrich Gun Parts Corp.they should have what you seek.
Inside the crane or on the slide
http://www.e-gunparts.com/productschem.asp?chrMasterModel=0860z788
Try a want ad or a gun show.
Up to 9 depending on model.
$100
The correct answer is Numrich gun parts. Or, just google Marlin A1 schematic and it will show you a list of parts that you can order and a complete schematic to view.
Impossible to answer without a detailed description.