Definitely remove the motor first. Close the bed and tie it shut so the center of gravity is over the press feet. With a 12×18, you need to have a 36″ doorway at least and you still may have to take off both the flywheel (on the left side) and the gear (on the right side). For my 10×15 that meant removing the entire crankshaft. For the 12×18, it meant staying in the garage for now.
Be careful with the truck/trailer. The weight capacity of the trailer does not necessarily mean it will hold that weight as a point load, which is what you need. Our trailer would not hold it. We ended up using a flat-bed tow truck to put the press on (on a pallet jack) and then put it from there into the bed of out F250. The truck held it, but we will now be replacing the entire truckbed because the load at the wheels of the pallet jack created 4-6″ deep grooves as the press rolled to the front of the truck bed. Like I said… not an easy move. It was easy to get out with a forklift (and chain hoist as back-up to prevent tipping), but you’ve got to be prepared for whatever it takes.