You can check the yellow pages for gunsmiths or browse the tables at gun shows. You might find something that will fit or can be made to fit, but you will never find anyone with a supply replacement parts. If it was made prior to 1900, it probably has twist steel barrels and was designed for 2 1/2" or 2 9/16" black powder shells with rolled ends. Using 2 3/4" smokeless ammunition with crimped ends is NOT recommended. Clean it up and hang it over the mantle as it is. Your granddad's homemade stock is part of its history.
100-300 USD or so
Impossible to answer without a detailed description of ALL markings and features.
200
Probably HD Folsom
I would start my search at Numrich Gun Parts Corp.They may be found on the web.
The Book of Colt Firearms has what you are looking for.
You will have to seek a qualifed appraiser.
Gun shop, gun show, pawn shop, want ad
Try e-gunparts.com
Up to $150 as a decorator piece. Thank You
I have a 12 ga. double barrel side by side shotgun made in 1936 and a while back I saw it in a book, it was worth about 1800 so I dont know if that helps or not but its a start
The duration of flu shot side effects varies from person to another.