JMRI can be very simple if you want it to be ..
Bring a car with a load to the industry you want - -- it automatically changes the load to empty and makes it available to go elsewhere -- unlike the car card system, JMRI will move cars around sort of like the railroad .. if you want an empty box car, it schedules one to go to the industry. If you have a load, it will send it to another industry (even off layout ie staging or storage) that can accept that load ..
Initially start simple - JMRI has a sample layout .. play with it .. don't be intimidated