I've endured the same aggravation, but it's the nature of these rear diesel models that don't have the side radiator and the convenience of the more accessible input locations.
While I've used the 'self' method, and then had to deal with 'what to do with all this oil', I've decided that letting the likes of SPEEDCO drivethru service do it is a much easier and less worrisome time. Yes, it's money, and I'm one to want to keep it in my pocket, but, then again, I see the value in letting the professionals with all of their tools handle it easily, even for the generator.
One problem I have, and still continues, is not being able to remove the main FUEL FILTER. It is plastic. You are instructed NOT to use a 'belt' type of filter remover, but the bottom 'tool removal' section still does not allow us to remove it. Even the professionals couldn't remove it, and were afraid they would break it and have diesel everywhere. So, it still works and still is the same filter that's been there for over 70,000 miles.
I also changed my own transmission fluid, which was actually the easiest of all, even easier than the generator.
two Campers, two Electric cars
former diesel pusher traveler