FWIW, after the fact... If you have troubles like that in the future, it couldn't hurt to ask for a local to help in open forum.
I do admit, I would be hesitant to take on a big job I wasn't certain I could perform in a timely manner. I also would be willing to donate a few hours if my schedule allowed it. I'm pretty sure there are other like minded folks here. I'm busy, I'm slow... but if nothing else, I might have been able to help you figure out shipping.
Future use... it would have probably been cheaper to fly round trip and use Fastenal to ship it. That may have been my solo mission plan.
Pure speculation, but since the seller did have a MH driveline for you... I'd guess they either switched the one that ran or left it outdoors. you might find it will turn some with plugs removed if it only recently got wet. We get a lot of rain, and it doesn't take much to hydrolock an uncovered engine. Pulling the heads is better, but will take a little more time.