They are only expensive if you are going to pay a shop to do it.... You can get a complete rebuild kit for a 4-53 for about $1200.
One cool thing about the 2 cycle DD is they dont have a central high pressure and high price injector pump just a continuous loop fuel pump and the injectors are mechanical... rocker activated plungers... you can loose an injector or two and they just keep running! The 2 stroke DD date back to WW II developed for the armed forces as a simple and reliable engine.
You can also thumb your nose at the Oil Barrons! How? In warm climates you can run the Detroit Diesel On well filtered waste fryer oil or in cooler climates Preheat WVO & Block.... Google treehugger they ran a 2-71 generator on strait WVO for 40,000 Hrs (if my memory serves me) then donated it to a NY Museum were it's still chugging away!
FREE FUEL!!!

None of us are as smart as all of us.