+1, simple. Don't over complicate it.
As for oil change intervals, unless you are running a really serious engine and abuse it lots, there is no real need to change the trans/tcase/rear end oil yearly. Well unless you drive ALOT.
See, unlike an engine, there is no combustion going on in the unit. its the combustion and gasses/acids etc from the combustion process that contaminates engine oil. Auto trans need more frequent oil changes too, as they have clutch slippage and they get VERY hot, then cold, then hot again lots. The heat and the clutch material is not good for the oil, but its not as bad as combustion by products.