Twostraight, I think Ill send any perspective seller your way so that you can pay that 90% spot. It will be a good chance for you to put your money where your mouth is. By the way, if you will notice, there are plenty of threads on here asking for advice. This, however, is not one of them. In fact, where I come from, this sort of thing is considered down-right rude.
Well, those old coins are worth what that guide says they are IF someone is willing to pay that much for them. A few years ago, I found some late 1800s to early 1900s U.S. coins in like-new condition that my wife's mother had and took them around to coin collectors and the like. What "the book" conservatively said was worth several thousand netted us several hundred, some of which was used to pay for the fuel I burned driving them all over the area.