Neither I nor anybody else involved in the farm have any mechanic's training.  My brother started working on cars as a kid, Dad is a good self taught designer/fabricator, and I'm just too cheap to pay labor rates.  I / we have done a few projects that aren't super technical but I'm kinda proud of having done ourselves.

Water pump on Cummins ISM.  Nothing like a water pump in a Dodge/Ram 5.9/6.7.  Those were easy 30 minute jobs.  ISM is a PITA if you've never done one before.

Water pump on Ford 8340 (7.5L).   Simple, but what a stupid design.

Ford 8700 injectors.  About as easy of an injector job you'll ever find.

Clutch on Ford 5600.

All older tractors and mostly big pieces.  We've never opened up an engine or transmission.  I'm cheap, but I don't want to cause more problems than I know how to fix.

R+R parts anybody can do.  No need for special training for a lot of what we tackle.  Some things take a few days that if we weren't learning as we go could be done a heck of a lot faster.