With some photos, it would be a lot easier to have an idea what kind of stamp collection we're talking about.
But I have to tell you that there's a strong likelihood that your Mom's collection is worth very little, perhaps basically nothing. There may be a lot of stamps involved, but they're probably all modern stamps, am I right? If unused, they're worth about their postage value, but dealers won't pay that much for them. Might as well use them on outgoing mail. If used, they're worth less, but that's very little. If there are First Day Covers, souvenir sheets, etc, there may be some added value. If there are many foreign stamps, you never know about value, but modern foreign stamps are also very, very common.
What most people put away from stamps they come across, even over many decades, makes up a large part of the collections dealers are asked to evaluate and a few stamps here and a few stamps there end up nearly always worth next to nothing, not even a hundred dollars in many cases to a dealer. If it's a well organized collection in an album, that might be worth a bit more. If it were my mother, I'd dispose of it (give it to a school?) and tell her I'd sold it for X dollars, and then I'd give her the money from my own pocket. That would make her feel she hadn't wasted all that time and effort. Or put it all on eBay
. That's one sure way to see what its value is. Sorry to be so sobering, but it's a common situation, and you shouldn't expect much.
Now watch. It will be a collection of rare old stamps, 19th century covers, and well filled albums, and I'll look like a fool! But I doubt it.