I’m not trying to talk you out of doing the work yourself I can only this information from growing up in boatyard hell and my observations from watching the diy process. If you are going to do it make sure to clean up as you go. The heads are heavy, have very sharp edges and things get slick with oil and diesel in a hurry. I had a customer drop a 6-71 head on his hand and it mangled it. There’s also times that I saw owners pull an engine apart 3 times and it still would spin a cam bearing after about 3 minutes of run time. The only way my Dad would do it for a customer was pull the engine, send it to a dealer and let them rebuild it and test run it. If you do decide to press on you are going to need a set of a-frames with a stout cross bar and a pair of quality come-alongs. We used a length of 2” shaft material. You also need to shore up the floor. You can cut 2x4’s and brace from the stringers. Once you have the engine lifted it’s not much more work to set the engine on a cradle and roll it out the door on pipe rollers. We had our old hoist set up with a pair of I-beams where the straps go and a long I-beam with a counterweight to reach in and lift the engine out. It was an Algonquin that was on rails that was electric so it was very controllable and quiet so you could hear the spotter. Check around and see if something’s available to get the engines out. That’s a lot of heavy iron.