Cost is all over the place.
Your labor or someone else's?
New head?
Used head?
Used engine?
You can take the head off, strip it down, and have a machine shop do the magnetic flux trick on it, to see cracks, but I can tell you that given the locale of the fuel channel in the head in relation to the inner water jacket, you may not even be able to find a crack... and even if you did, may not be able to be repaired anyway.
Also, fuel in the cooling system will have done some damage... basically EVERY cooling hose, possibly the radiator, possibly the heater core, could be subject to failure. Rubber and plastics designed for coolant do NOT like diesel fuel.
If you got the car for free, and you had to spend $4k on the car, you could potentially have a decent car for a decent price all said and done. But if you are looking to spend $2k on the car, and fix it for $1k, you are likely going to be disappointed.