To get the engine out of the boat you have several options.
1) Build a frame over the boat using a 4x8 beam and some 4x4 legs. Lift the engine up using a come-along or chain hoist. Pull the boat/trailer out of the way.
2) Get the engine all disconnected, take the boat/trailer down to someplace that has some overhead anchor point. I would be tempted to find an empty industrial building that had a loading dock with an overhead I beam. Back the boat up, attach you chain hoist, pull the engine, back a truck in, lower the engine into the truck, drive away!
3) Many boat dealers have a crane that they use for lifting new boats off the delivery truck. You might be able to work a deal to use their crane to lift the engine out.
4) If your boat is still operable I would go to the "find a third" part of these forums and offer free pulls to anyone who has a backhoe or forklift.
I would recommend option 1. Getting the engine out is the easy part, getting it back in will be a bitch. You are going to want to be able to take your time while you get the engine mounts figured out.