I wouldn't worry about a 30(ish) years old watch. If you get it in good condition chances are you won't have to do much reconditioning. As for the gaskets, if I found a good watch that needed ONLY the gaskets replaced I wouldn't hesitate for a second.
I'd say go for it. You might be amazed by how much these watches can take. They're resilient... Just because it's a quartz doesn't mean it's easier to break down.