"If I were" is correct in this case, as it is using the past of the subjunctive mood, which is used to express an imaginary or hypothetical condition. That sentence is similar to the following ones, which both are using the subjuntive mood.
If I were rich, I would live in Hawaii.
I would live in Hawaii if I had a job there.
The NOAD reports a note about the usage of the subjunctive mood:
if I were you; the report recommends that he face the tribunal; it is important that they be aware of the provisions of the act. These examples all contain a verb in the subjunctive mood. The subjunctive is used to express situations that are hypothetical or not yet realized and is typically used for what is imagined, hoped for, demanded, or expected. In English, the subjunctive mood is fairly uncommon (especially in comparison with other languages, such as Spanish), mainly because most of the functions of the subjunctive are covered by modal verbs such as might, could, and should. In fact, in English, the subjunctive is often indistinguishable from the ordinary indicative mood since its form in most contexts is identical. It is distinctive only in the third person singular, where the normal indicative -s ending is absent (he face rather than he faces in the example above), and in the verb to be (I were rather than I was, and they be rather than they are in the examples above). In modern English, the subjunctive mood still exists but is regarded in many contexts as optional. Use of the subjunctive tends to convey a more formal tone, but there are few people who would regard its absence as actually wrong. Today, it survives mostly in fixed expressions, as in be that as it may; far be it from me; as it were; lest we forget; God help you; perish the thought; and come what may.