The tax-exempt status of faith healer Benny Hinn's $6.5 million world headquarters in Grapevine is being examined by the Tarrant Appraisal District after a televangelist watchdog group this week questioned whether the property should be considered a church. The review of the property at 3400 William D. Tate Ave., triggered by a requset of the Dallas-based Trinity Foundation, is considered somewhat unusual, appraisal district officials said. But any requset for a review is investigated as a matter of policy. ...Trinity contends that the ministry hides its spending from donors and uses donations to provide Hinn with a multimillion-dollar California parsonage...