Yanmar 4jh4e life expectancy

[RCP Trader]

Hi fellows,

I am looking at this sailboat 2008 Jeanneau with 4200 hours.

Rumors has it the hours are not correct. Is it possible to over mark the hours?
Did it serve most of its life expectancy? The service was moderate, not much records available.
What's the cost of dropping in a new remanufactured engine or overhauling it. That is when the time comes. It currently runs fine, sounds smooth the smoke is normal.
Does this model have a computer to run a test? Is there a compression test possibility?
The oil test iron came back 28, aluminum 4 and copper 42

Sorry about all these questions, and at this.
Thank you in advance