Part of the equation might whether you are comfortable with holding a wrench, screwdriver, and if necessary a hammer.
If you've never worked on a Diesel before, you'll learn about injectors, glow plugs, and AIR very quickly.
A diesel is just like a gasoline engine, but without all the electronics. Ok, not quite, but don't let a $300 diesel engine scare you. It certainly would be a good tractor to practice on before investing $300,000 in your next tractor.