I saw a decent deal on an used Apple LED Cinema Display (Display Port 27") on Craigslist. The seller is upfront telling me that the LCD screen, power supply, and logic board had all been replaced (over a single incident) by Apple because of buzzing. Have receipt to prove work done by Apple and not anyone else. Never bought an used monitor with a repair history. Is this risky? What should I look out for? The monitor looks great on the outside. But I just don't know enough about buying previously repair Apple products of this kind. Please help!!!