Probably not. There has never been a scientific study showing a statistically significant effect of ginkgo biloba on tinnitus. However, if you take it and feel better - great.
Yes. An audiogram should be done to show presence or absence of a hearing loss. Gingko biloba is less successful in helping tinnitus in presence of a hearing loss. Gingko biloba has been reported to be helpful for vascular tinnitus. You needs at least 120 mg/day and i instruct most patients to use it for a minimum of 3 months. It should not be used if you are taking any other anticoagulant meds.