Engine Rebuild Cost

[TPIJeep]

Looking at buying a 2001 Honda Forman 450 ES, the kid ran it under water and hydrolocked the engine, didn't tell his mom and it has sat for a few days... we flushed the oil 4 times, ran marvel oil on the top of the cylinder and got it to run.. However it is smoking...

Any idea what kind of cost I am looking at to have a Honda store rebuild the engine? I plan to do the work myself but am interested in what the Honda place would charge her is she took it in.

Thanks