There is one way to learn, go do it right. If you have a link to the boat listing if there is one post it. Tartan, especially of that age are great boats, sturdy, overbuilt, and pretty to boot...better than decent
I would get a survey as already suggested, just like a house, it good to have someone go over the little things with you and more than likely they will see things you wouldn't.
Keep in mind that once you take that leap there is a good chance you will spend many more boat bucks outfitting to your liking, repairs, storage, mooring/slip fees...but all worth it if you enjoy the experience.
Last thing I would suggest is you take it slow, don't be to aggressive with you planning so that you don't end up overwhelming yourself or crew and worse getting into an unsafe circumstance. Travel with others if you can until you feel comfortable with the boat and your skills.