OK, I'll talk slowly...

As far as I can tell, the RTR comes ready to run.

To be absolutely sure, I would send them a mail, asking them to state what comes with the boat for 645 Euro (sixhundred and fourtyfive!) and what you need to buy to get it running (radio, receiver, receiverpack, maybe even a controller and batteries).

Yes that's the Lehner motor.(brushless)needs a special controller(one with two thick wires going in and three thick wires going out)

No, the RC-Hydros ESC is not compatible with this motor, it's meant for brushed motors. (only two thick wires going in and out)

Let me know how things go.

Regards, Jan.