A grand piano is a specialty movers' job, full stop. Its case can weigh 500 to 1,200 pounds resting on three legs and a thin, curved soundboard under enormous string tension, and the standard technique lowers the whole instrument onto a skid board with a minimum of three trained movers. Hiring a professional here is not caution, it is the correct answer.
Pro tip: Ask any quoted piano mover directly how many grand pianos they move in a typical month; genuine specialty companies do this regularly and will answer without hesitation.
Watch out: Never hire general movers or attempt a DIY move for a grand piano; the case alone can weigh 500 to 1,200 pounds and the soundboard is thin, curved wood under tension that a careless drop can crack beyond repair.