Looking up at the PTO bolt from the bottom it removes counterclockwise like a standard bolt.

Best bet is electric or air impact wrench with an impact rated socket.

When the bolt comes out the PTO clutch may freely drop... WARNING... it is heavy and can injure you or damage itself..

You do not have to remove the flywheel nut, nor the flywheel, to remove the engine. Just make a sketch of where the electrical connections go, when installing the replacement engine. And, as the other poster sez--use an impact wrench to remove the electric clutch on the lower end of the crank-shaft. Be careful, tho--it is heavy and will drop quickly! Then remove the four mounting bolts. You may have move the clutch pedal somewhat to access one or two of the mtg bolts. It might be best to remove the hood for better access.
Note: If you remove the engine sump, to replace the gasket--DO NOT use the sealer that ya buy in a tube! Use the paper gasket that you can buy at most mower parts places. I have used several small blobs of wheel-bearing grease to hold the gasket when reinstalling the gasket-smooth it out, and press the gasket down onto the block. Then install the sump. The BLUE GOO doesn't hold up for long and will leak eventually!