J.S.
As a pianist, I would NOT do it sight unseen. It needs to be seen and at least played so that you know what you'd be getting but since you don't know pianos you would have to bring someone from a music store who knows how to play and tune pianos.
You also have to consider that anyone who moves it has to know what they're doing in order to cause the least-to-no damage. It WILL need to be tuned after you take ownership of it. It will need relatively frequent maintenance.
What it comes down is that you're not really getting a free piano. You're paying at least $600 to transport it AND you're going to have to pay for tune-ups and very likely some repair. You may need to get strings, pedals, pads, and other inner workings replaced. You could very well end up paying far, far more than $600 in order to get a working piano.