One question about the head gasket issue. Is changing a head gasket on a diesel inherently any more difficult than the same job on a gas engine? I've done the latter a couple of times, and I fully realize that a blown head gasket make simply be a symptom of a much more serious problem, but I was wondering how big a job changing the head gasket itself would be on a diesel. Who knows, my Yanmar may need such "surgery" in the future.
Compared to an automotive engine, it is much simpler. the intake and exhaust manifolds are simpler, there are no emission controls, no accessories mounted in the way (with the exception of the alternator,) no timing belt or chain to remove, so no cam timing issues upon reassembly, the head can be disassembled on the bench, rather than having to unplug the injectors and remove them in situ.
I have not torn the head off any car newer than 1988, but I have wrestled with everything from E-type engines to old Bentley lumps to Daimler's gorgeous little 2.5 litre hemi v-8 to more VW and Porsche aircooled engines than i can count. Based on that experience, dealing with rusted and busted old fasteners, I figured i would need 12 hours to R and R the head of my yanmar GM10, including new valves, new head gasket, new exhaust gasket, rebuilt injector. I had the head off and out in less than 1 hour, 2 hours on the bench, 2 hours to get it back together, requiring a total of two screwdrivers and 3 wrenches. Up until that point, I liked that little diesel. after that job, I loved the simplicity- diesel engines have only enough parts required to make it run, and they don't need much to run.