Unless your grandfather already has done this, you will have to pay to have each you want to sell professionally graded. You can then find a wealth of online and bookstore or library resources to determine what the typical market value is for each, and then pursue listing them for sale in appropriate sites.

I think you are being foolish in your approach. You know nothing about stamps and collecting. It would be well worth the money it would cost you (from the sale) to have this evaluated and sold for yoru professionally. It will be quick and not take much of your time and effort at all (that's what you are paying them for).

Also, since you don't mention anything about the insurance on this collection, I get the impression that they are mostly just interesting stamps and not extremely valuable. Unless you have something really, really rare in there, I wouldn't expect to get more than a hundred or two for 2,000 "interesting" stamps.

Seems a shame to lose this legacy just so you can go buy some cheesy video game that will soon be forgotten or obsolete. Why don't you think about enjoying looking at each and maybe finding out something about them, and holding them for your heirs to pass on to them? A lot more intangible value there than the paltry few dollars you might realize on a sale.

Go to the book store, and buy a book on stamps. Or look them up on eBay, and see what they are selling for.

Trying to sell 2,000 stamps individually sounds like it will literally take years. Unless you like this sort of thing (and maybe you do), sounds like a hassle to me.

Take it to a pawn shop

Ask a stamp expert.

My great-grandfather had a huge stamp collection, and his dying with was that the 4th generation to inherit it sell it and use the money for something useful. How can I study each stamp and sell it for the right price? And where? I'm not selling it to a collector because I will lose a lot of money, I am selling them all individually for the right price. The estimate total is around 2,000 stamps.