Thanks for all the replies! We kind of have to pull a trigger to meet other deadlines, not wanting to end up stuck at the side of a mountain road or anything. So I went with the rear axle, the transmission fluid, the brake fluid, and the power steering fluid at the Ford Dealer. There's a separate place I can get a flush/fill on coolant for a lot cheaper. Mind you, we aren't having any real symptoms other than some occasional squeak from the brakes. But, before heading into the mountains it seemed prudent.
I too am of the opinion that the spark plugs don't need changing yet, or at least, not at that price. @myredracer, yes, I knew it was something like that. I had platinum tipeed plugs on a Honda that were still working just fine after 150K, so I don't plan to push a panic button even at 100K.
Unfortunately, even in a huge metro area like Dallas (6.5 million people) I haven't found many places to have it serviced since we got it in October. We're too big for the usual Ford dealer and like I said, a lot of RV places are either focused on coach work or booked up at the moment. So we'll throw some money and hope for the best.