She wants $30 for a baby grand?
Does it have any keys left?
Seriously, this isn't likely to be a piano. It's likely to be firewood. I'd be tempted to buy it anyway, because for $30 you can get a real fast tutorial in just how complicated this "most complicated of any machine ever made" can be. It would be a hoot if you had a place to keep it, rip into it and learn about the action and so forth. A cracked soundboard is likely to be the least thing you would have to worry about.
For instance, you could try to tune it. Then you would learn why a tuning wrench is called a "tuning hammer," and why the reason it won't stay in tune might have something to do with that big crack you see on the pinblock with all the hardened epoxy goop coming out of it - the one the piano technician will charge $20 to tell you can't be fixed. (Hint: he's being kind).
Are you still sure you want to do this? 
Most cracked soundboards still sound as OK as the rest of the instrument will allow. Usually everything else has gone to hell so the soundboard is pretty low on the priority list. The bracing is crossgrain so even a cracked board isn't likely to go anywhere. To look at it, you get on your back underneath the thing and look up. The "floor" on the other side of the frame is the soundboard. The cast iron harp (or frame) on which the strings are mounted is bolted to the case, and the soundboard will be immediately under the harp. The strings break on bridges mounted directly to the soundboard, as on a guitar.
Be VERY careful moving this thing, as you can get
badly hurt.
The legs come off. You can flip it on the bass side and move it on a dolly. Or two. Or onto a board sitting on a dolly, then rope or strap the thing together.
You can actually tip it over without doing any harm. FIRST YOU TAKE THE TOP OFF (meaning remove the hinge pins and physically take the lid and the sliding music desk into the other room) and then you lift on the treble side and keep going until it is completely on its side. Look at the legs for individual markings, as they are not interchangeable. There will be cams clamping them in and iron castings holding everything together. Watch out for cracked or broken castings, as the thing can let go when you try to put it back upright, and all of a sudden you can be the one holding up that particular portion of 600 pounds. That's not where you want to be. So don't try it alone.
Don't move it in a pickup truck, or you'll have to build a frame to keep it upright, like I did, and you will probably run into a thunderstorm, like I did. Just don't use a pickup truck. Get a panel van and rope or strap the sucker tight to one side of it.
It's a big operation, and you can sometimes find a mover to do it. Then you see that they actually earn every penny they charge.
Or, if you want a piano to play, maybe the thing to do is move to a decent used electric for now.
