Well, lets say you have to have new pistons
but the rods and crank etc. can be refurbished.

My personal perference would be to definitely replace
pistons if you take the head off of an unknown mileage
engine unless you were an expert at diesel piston wear.

Given the head needs to be ground, valves reseated
and sealed, etc.

Given all the above, What would be the $$ cost of a dependable independent shop
performing the work.