The real question is, how much time and effort are you going to put into this outside your tutoring sessions. I'd say an hour a day is the minimum, with two hours of course better. The point is, that unless you dive into this at the beginning, your progress will be so slow that you'll almost certainly lose interest. When studying languages, I've always found that positive feedback -- getting a sense that week by week my skills are improving -- is important to create the incentive to keep at it.

Two or three hours a week with a tutor isn't that much, and as for texts you'll need something with good and extensive tapes. Myself, I found he DeFrancis series as thorough and complete as possibly could be, but the dialogues are quite dated and that puts many people off.