I don't know if they've changed it, but front and rear differential used to be very easy on Subarus.
Rear differential is like most differentials, clean it off, remove the fill plug, remove the drain plug and drain the oil, return drain plug, fill with oil, return fill plug.
The front differential is like an oil change, you drain from below, return the plug, then fill it from the top. You fill it through the front differential dipstick tube that's located in the engine bay. It's low down near the firewall on the passenger side of the vehicle.
The CVTs are a different story. Last I heard Subaru says to take it to them for all servicing including a routine drain and fill. If I recall correctly, there's no way to check the fluid level, so you have to measure what comes out during the drain, and then fill with that much clean fluid. Subaru has some machine/process of doing this to measure how much comes out. That being said, I have read on forums of people doing it themselves on their Subarus.
I wish Subaru would've made the CVT more serviceable to DIY owners. Either a dipstick for the CVT, or having the fill hole on the side as opposed to the top so that it'd be like a differential fill hole, just fill till fluid starts to dribble out and that's when you know it's full. I'm not an engineer, so I'm not sure if that would work for something as large as the CVT pan, but whatever the necessary solution is, I wish Subaru would've made their CVT more self serviceable for the owners.
