Your whiskey should still be drinkable, as alot of even older bottles still are.
However, you may find the taste a bit "oxidized" if there has been a significant amount of air in the bottle.
As for valuation, for that I'd have to see photos of the bottle to know it's condition & fill-level, and to get an accurate date of manufacture.
If you need any help, just let me kow!
Walter C Hurst