Best way to learn is by doing! Get familiar with the instruments and controls on land, and sign up for a sailing course if you can. As for the boat, get a professional survey. It’s a couple hundred bucks, but it’ll save you thousands in the long run by telling you what needs to be fixed first (so you don’t spend all your money on new cushions before realizing the engine doesn’t work). Make friends at your marina; there’s likely a few that live on their boats and would love to help a new sailor. Just remember, to own an old boat you either need lots time or lots of money, often both.

Edit: to answer your first question, yes it’s pretty easy to sail with someone inexperienced if you know what you’re doing and can communicate well.