Bring a sawzall and cut away about 2 inches from just under the stairs. Don't cut the fiberglass at the bottom of the engine hatch, thats structural. Pulling it out is doable the other way, but you and whoever are helping you are gonna have a much better day if you cut it.
Take the mounting studs off completely, don't think that when you put the engine back in the alignment will be magically right if you just leave the mounts.
You can not get a new 1gm10 in the US, they don't have a valid emission certificate.
Where are you located?
Its not a super easy job, but not that hard either, I did mine with just the main halyard restrained by the outhaul. We tried to use a chain hoist, but it was not easier, and the winches had plenty of power for the job. Took about 3-4 hours from start to finish to pull the old, and install the new.
Bring a couple friends, Ideally a very strong young guy, and a bunch of beer and be prepared for one or 2 people to be doing work while everyone else sits around for long periods of time, but every now and again, 8 hands will be really useful.
My coupling was fairly new. If yours is old and rusted you might want to work on getting that cracked off before you even start to think about pulling the engine. That might be an all day exercise in bruising your knuckles.
Good luck!
tim