Willow51674 - I agree with what was said so far. Most collections, including mine, are worth much more to the collector than anyone else.
The one thing I don't think anyone has mentioned (sorry if I just missed it) is that if you really want to know what the collection is worth, you might take it to a stamp dealer. You can probably find one or two near you that would be willing to give it a quick lookover and a ballpark figure. They may be getting few and far between, but it is still a stamp dealer's job to know what stamps are worth. There are a few willing to sell their soul to make a buck but I think the majority build their business on reputation. If you think they are low-balling you, get a second opinion.
Another option is putting the entire collection or groups of stamps at a low reserve on
ebay or the like. If a couple buyers notice something truly unusual, they may bid it up to what it is really worth. That probably will probably be less than "catalog value", which is really just a reference value for dealers. Stamps from dealers are often actually sold for less than catalog value.
Of course, just continuing the collection might be more fun
