What model?
Loosen the grip screws.
Best source of information is the Standard Catalog of Smith and Wesson, 3rd edition.
With no more than that to go on, the best I can give you is a range of 300-3000
You can request an owner's manual for free at S&W's website.
No
Frame and bottom of grip
One has been.
No
Not likely
CHeck with the maker of the grip.
Can't be answered without a DETAILED description of ALL markings, barrel length, finish, grips, sights, box, accessories, papers, condition.