Repair or Sell Grand Banks 36 Classic

Fellow Boaters I have need of your help.
My Lehman 135 overheated (loose fan belt) and shut down. We had to be towed in.
The engine would not restart. Flywheel will not turn. Slight smell when the valve cover was removed. No water in oil. Expansion tank holds coolant.

Bottom line, getting an engine out of a Grand Banks is not easy. I have done it twice. But the engine should come out to be repaired. (My mechanic) He suspects broken shaft.

Cummins has an engine, 6BT Retro I believe, that has been known to replace the hard-to-find Lehman engine in decent shape. Cost around $10,000. I figure the replacement costs including on-the-hard would be between $15,000-$20,000.

So here is my dilemma:
Wife wants to sell. Tired of engine swapping. Does not want to spend another dime, sell as is.

I see on the boards, Grand Banks are a desired boat, running.
Not sure about not running.
Should I repair, go through the trip to the yard, spend the money and then sell
\or
Sell as is and take the hit?
Your thoughts?

Boaters, Thank you for your input. I have been a quiet follower of the two forums I have posted in for years.

The boat is a 1979 36 Classic. We had the bottom redone 2 years ago, blisters, paint and all. 6 solar cells for power on the hook. 6 new batteries, 4 for house and 2 for start. Nice diesel generator. 2 A/C units. New "Natures Head" marine toilet, new instruments, fly bridge has hard top, all new interior, bedding, stove, etc.
Maybe if running: $75,000.

My thought was to start with the price, minus estimated costs for repair, but that is hopium on my part. Without sea trial or running engine, might as well give the boat away.
The mechanic is a marine mechanic, and the question then arises, how far do you dig into the engine before you call it dead?

Working lubricant into the cylinder heads sounds like a good course of action.

No, the engine did not run for long, maybe 2 minutes, before we shut her down. I misspoke by saying the engine died. There was steam coming from the engine room, temp got to about 220. I have mechanical and electrical gauges as well as a laser heat gun to monitor the engine heat. Ran fine at 1750rpm. When we opened it up to 1850rpm, all hell broke loose. I shut her down. IN hind site, probably should have just idled down. But that is history.
There is my story.
Love the boat. DO NOT want to go through taking it all apart on the hard.

Again, thank you for all your input. This is a real pickle I wish was not in my jar.

See my new post for your answers. Thank you for your input.

One last piece of info on my GB 36. The Lehman was a rebuilt RTO. She only has 35 hours on her. Had the engine installed one year ago.

All hell broke loose - steam, shouting to drop anchor, idling down, realizing the shipping channel on the St John's now had a disabled boat at the Dames Point Bridge.

No banging, no noise, no indicator, no nothing. Just went from 180 degree to a little over 220 in about 2 minutes.

I was running between the two helms checking the new gauges and comparing them to the laser gun and mechanical heat gauge.

I was still "breaking" the engine in, slow is better.

We have had the boat over a year from the install. That would be another can of worms to open - trying to get the mechanic to own this failure. Yes, it could be shoddy workmanship, but that is the old water under the bridge.
Thank everyone of you for your help. Just "talking out loud" with other boaters v my wife only, has helped me see the bigger picture of what might be ahead.

Did not hire a mechanic surveyor. Engine froze and banged very loud on our start up to leave after the sea trial and contract sign. We never found out what caused it, leaking exhaust back into the coolant. Previous owner literally shrugged his shoulders and got in his car and drove off. Finally came down to finding another engine. A Lehman in good shape is very rare. Found RTO in Miami. Put it in. Found an oil feed into one of the cylinders installed backwards from the rebuild. Take out and do again. 35 hours later, here we are. There was no sound with this failure. I just went worse case scenario after the 2 years it took to find and get the engine installed so the boat would at least go forward in the water. I have been inspired by the posts above. I am going to roll up my sleeves and see where it takes me. Will keep you informed as to how this goes.