I recently bought a 19ft Stingray SS in pretty much perfect condition
except for the engine. It has a cracked block. I've ordered a
replacement long block 4.3L marine engine. It should be here in a
couple weeks.

I've never replaced the engine in a boat before. It looks pretty
simple and straightforward. But I have never seen how the outdrive
attaches to the engine. Does it have a torque converter or something
back there that just slides out? How are the engines and stern drives
connected? If I undo the bellhousing bolts it should just pull apart,
right?

Any special advice or tips that would help me along?

And where do I look for the replacement gaskets? Is that something my
local boat dealer could get for me? I would suspect so, but it never
hurts to ask.

Last of all, what should I use to actually remove the engine and place
the new one in? The boat is way too high and big to use an engine
hoist. It's not really possible to make a crossbeam and raise it that
way since I have no access to large enough poles and wouldn't be able
to put them in straight and all anyway.

Would a rented backhoe type tractor do the job? How much does a 4.3L
marine engine weigh anyhow?

TIA