Thanks so much to everyone. Especially Raventepes for your post # 17 with the diagram. It did help, and the Nikon Simulator was a good aid. I get the telephoto/wide angle issue. Having a little more trouble with the FX vs DX, but that's ok, I will learn it over time.
I hear you guys on the negatives of the 18-270 lens. My concern is how, with little experience I have, will I be able to determine which lens to use, and quickly change back and forth to capture shots, if I pick up the 70-200mm, on my trip to Alaska? Maybe that's a dumb question borne out of ignorance, and I am making things to complicated.
So here's a stroke of bad fortune.... I took another lesson this week. And walking around in the park to shoot, my camera, which was slung over my shoulder, fell to the floor. Turns out I didn't secure the strap properly. It seems to work fine, I am able to shoot, and use all the functions. So I was relieved. But when I took the camera in today, to buy the Tamron lens, my 18-55 wouldn't come off. The store (professional photo shop, not a Department Store) told me that apparently when I dropped it, the lens mount was damaged, and I would need to send it to Nikon and they would probably charge me at least $200. (then he proceeded to try to sell me a new D5500)I want to shoot myself. I am leaving for Myrtle Beach next Sunday.
I happen to live 30 minutes from the Nikon Melville NY facility, so I plan on driving out there on Monday morning and seeing if I can get it fixed quickly. And maybe since I've only used the camera a few times they will have sympathy on me and fix it under warranty (but I doubt it).