depends on how trashed the engine is, go to the market and get some parts quotes, regular stuff like
bearings, rings, gasket set, timing set, valve guides, nozzles, assembly fluids etc.
then to to machinist and ask for rates of work of valve job, bearing regrind, cylinder work etc,
then pay a visit to a diesel lab and ask for calibration of the pump and nozzles.
add up the charge, then ask mechanic of his charge with disposable parts like cleaning stuff.
add 15 to 20% more to the price of what you get in total.