on #2) I think a majority of the headgasket issues is from either poor maintenance, or heavy heavy usage.
apparently, there is a domino effect that can start with the head/HGs, oil cooler, or egr
-if the oil cooler gets plugged up, the egr
cooler will fail & then you get coolant in the intake, thus blown HGs or cracked head.
-then again, any time that the oil gets contaminated with coolant - oil cooler plugs up & all goes to crap.
also, if coolant gets contaminated with oil, then the egr
cooler plugs up & fails & all goes to crap.
-& in either case, i believe the turbo is susceptible since it's fed oil & spools up from wet gooey exhaust from the leak. & injectors are in danger too if the oil is contaminated.
i've been trying to figure out what all went wrong with my truck before i bough it lol! i'm thinking the egr
cooler popped a leak because of dirty coolant (poor maintenance by the previous owner), and that caused turbo to gum up (i think) and HGs to blow eventually...i'm guessing on this because of the service records i found lol
correct me if i'm wrong :)