I'm a wine idiot

[monanna]

I certainly hope some of you wine experts can help me and my wife. We have recently had a grandmother pass away...all her wine and liquor was passed down to me and my wife. About 50 bottles in all. The only problem is we drink wine only occasionnally. We don't know all about wine. The wines range from Chardonney to Rose Wines from Portugal. They date from 1971 to 1996. My first question is how do I know if they have gone bad without opening them? Secondly, does anybody buy wines that are old?