Freezer not cooling

I acquired a very old freezer from a friend. He got it last year and it worked fine, but it was probably manufactured in the 1960’s. I plugged it in yesterday and it was still at 85 degrees when I got home today. It is making a noise when I plug it in and the side of the freezer is warm, but it is not cooling. How should I start diagnosing the problem? I would love to get it working since it’s HUGE and to get a new freezer of this size would be fairly expensive. Is a freezer this old worth fixing if it is a major issue?