I don't think many of us carry spare starters or many pumps per se... certainly spare parts for any pumps you may have so that an in the 'wild' rebuild is possible. I'd also research and keep on hand contact info for any suppliers you may need to tap (that list does little good sitting at home). With cell phone coverage improving all the time, it's possible to have parts delivered (though possibly pricey - but so is a tow) if you can track them down to a source.
If you're comfortable with gas engines, then diesels are so much simpler that you should have no trouble.. got air? got fuel? got compression? - you're good to go. Generic parts like fuel lines and such should be no problem getting hold of.. and the external parts like heat exchanger bundles, RW pumps and the like are not necessarily engine-brand specific .
Sounds like you're as well set up as most already, if not better...
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)