IMO, the most important thing for a new collector is to obtain the newest copy of the book "Standard Catalog of Smith & Wesson" by Nahas and Supica. It is a veritable gold mine of information. Then spend hours and hours studying what is of interest to you. It is not intended as a coffee table book, but, rather, a text book. There are other valuable books available that should be in your "library", but this is a good place to start.
Believe me, the slightest little difference that you would not ever think about could mean hundreds of dollars difference in price. By and large, some of the more important things to know is serial numbers and locations. When was what stamped and where. When did such and such begin. When did such and such end. Barrel stampings and trademarks, locations and size of them. It just goes on and on.
As to your specific question about stocks, (S&W called them stocks, not grips.) if they are service or magna stocks, they should be marked with the guns serial number on the right stock panel. Target stocks were very rarely ever stamped with a serial number. So even with a factory letter that says this gun left the factory with checkered walnut target stocks, you will never know if the ones on a gun in question were the same ones that it was born with. If they are period correct, you pretty much have to assume they are the originals.
If the stocks are service or magna and they are not serial numbered to the gun, then the gun is worth less. Additionally, if the stocks are not even period correct the gun is worth even less. With few exceptions, if the stocks are not factory, value of the gun is even "more" less. If the stocks are un-numbered but period correct, most likely they are not original to the gun. But there is no way to prove it, one way or the other. And speaking of exceptions, there are exceptions to every single rule.
I can't believe how much knowledge I have gained in the past several years, and how little I still know. I have seen folks on this forum who have collected S&W for 50, 60, 70 years and are walking encyclopedias say "I did not know that."
Last thing I have to say about S&W is "Never say never." Someone will prove you wrong. This is what makes it so daggone enjoyable.
EDIT: One more last thing to say. If you are serious about collecting S&W, join the Smith & Wesson Collectors Association AND the Smith & Wesson Historical Foundation.