It always is wise to measure twice and cut once - applies to everything in life. To get the best result heres a breakdown.
1 - collect parts costings
2 - locate the parts - including all the proper glues/pastes/assembly lubes etc.
3 - look for a proper diesel service facility for calibrating the pump and nozzles like Toyota/daihatsu did when new
4 - gather all special required tools (either cut a deal with the mechanic or simply consider it as investment)
5 - make other plans to repair the engine room whilst the engine is out - e.g. repairing the whole wiring harness, repairing the sound deadening batting, repairing any missing clamps/clips etc, taking care of rust.
Remember that a car is a machine for transport, if you cheap out on repairing the machine the transport will not be reliable - Spooky.
To get a costing analysis - dont judge it by the current value of the car but by the value when it was brand new. Makes sense if the car is worthy to be rebuilt, otherwise scrap it.
the last paragraph may show you the problem with upkeep of these JDM orphan cars, people assume they are at correct full pricing and their spare parts should be cheaper than that, which is laughable, the spares pricing does not consider devaulation.