My 1981 H27 has a Yanmar 1GM that I just had rebuilt, two guys lifted it out of the boat by hand to work on it. If this one ran before and the boat wasn't sunk at any point, you might be able to get it going. If you do pull the engine, go ahead and replace the fuel tank, muffler and all the hoses while the engine is out of the way.
BoatUS required a survey before they would insure it, you may have to have one done for your insurance company. I still had the older gate valves on the through hulls which had to be replaced. Surveyor would be able to give you an idea of what shape she's in. At the least, the traveler, boom vang, and pedestal guard are upgrades I don't have.
You might get luck and she may not need all that much. Mine was a nice step up from a C-22.