Given you're not sure about the piano itself, I'd have some tens and a $20 or two discreetly someplace - put $10s in one pocket and $20s in another if you don't want to stick it all in another room and ask them to wait a moment, and just wait and see what the deal is.
If it's nothing much, they just carry it in, unscrew and replace a leg and are done in 20 minutes or whatever? $10 each.
If it turns out to be a monster that they end up taking doors off hinges, dissembling things or looking at your windows funny, have to wrestle badly with, and spend a lot of time working on? douple up.