You will need to provide a detailed description of ALL markings, caliber, barrel length, caliber, type of action, describe the stock, bayonet mount if any and how it is configured, sling swivels, if any, and location.
barrel, stock, action.
Barrel, action, stock
Stock, action, barrel
Very short. The action is back at the rear of the stock, and the trigger well forward of the action.
Stock
Look at the underside of the rifle, it will probably be stamped into the action up by where it meets the wooden fore stock. If it's not there, look at the metal tang that attaches the shoulder stock to the action. The number may be etched into that strip just behind the lever.
It means inserting a pair of metal posts (pillars) bwtween the trigger group and the action. See the link below on RIFLE STOCK BEDDING for illustrations of this.
Not much we can tell you with no information. Some rifles are marked on the receiver (frame) some military training rifles have marking under the stock (remove stock to see)
Look at the underside of the gun, the number will be stamped into the action by the wooden forestock.On some very early models, it was hand etched onto the lower tang that connects the shoulder stock to the action, just behind the lever.
100-1000 USD or so depending on specifics
on the trapddor rifle, to the rear of the receiver, just before the wooden stock
Remove the stock and you will see what is keeping the bolt from sliding out.