Tung oil is available at the box stores or your local hardware in the paint and stains department. Two major suppliers: Minwax and Formsby. It's actually called Tung Oil Finish, which is a formulated compound, not true tung oil, but it's what you want. I use either tung oil or boiled linseed oil depending on what I want to achieve. Each has it's champions, so I think you'll not go far wrong with either.
The key, like any good paint job, is preparation, Take your time, and if you're not sure, do it over. Don't be in a big hurry and expect to do it all in one evening.