Charliesmom, It's not as much of a bummer as you might think, just an incredible amount of history, experience and information to absorb, that can be daunting; don't ever feel rushed into the decision, or that can really weigh on your later. If you need some of the backstory, written in relatively easy to understand english, Ken Rockwell's site (kenrockwell.com) has a section for every body and lens made, including a comprehensive lens page for what lens will/won't/might work with any of the bodies. The thing we like about buying from a NY shop like Adorama, they physically inspect and check every pre-owned unit they sell, and have a 30-day, no quibble, return policy, that can't be matched elsewhere, and we've bought almost every way that can be had, private sellers, ebay, amazon, name it. Adorama has always helped us find what we need, or takes back what we don't).

If you buy from such a shop, whether your research tells you that what you want is either FX or DX, you'll have 30 days to love it or return it, even it it's a brand new one. The market is hard to grasp, as it can seem extremely overpriced one week, and depressed the next, based on supply and demand. The onus is always on the buyer to know what it is they want in a body. The two examples that I may feel strongly about, others have their strong opinions on. If you want a great camera, the D7200 has the two cards, can make videos up to 30 minutes (the card and battery will heat up), and it will use any lens. The D700 doesn't make videos, has only 1 slot, but takes in a larger chunk of territory. The viewfinder on the D7200 shows 100% of the image you're making, the D700 doesn't show quite as much, so you have to adapt. Always choose the body that can use a lens with or without a built-in lens motor, those two models have a body motor that works for non-motorized lenses. Any of them will do manual photography, and when it comes down to it, not limiting yourself to auto-focus means you finally reach the point where shooting manually can achieve results that's extremely hard to beat! As long as you're pleased with your work/images whatever format you use, you'll keep getting better. Good luck, sv

That's been an interesting read. My unsolicited advice is for you to do what you want to do and pay no mind to all the folks who ask the same old rhetoric. If you want a new or nice used camera, even though there is absolutely nothing wrong with your current one, go for it, assuming it is not a financial burden. I personally have been collecting cameras for many years. It didn't really start out that way but it turned out that way. I now have more cameras than I could possibly ever need but for the most part, when I upgrade I simply keep what I already have. I only own two Nikon DSLR'S, a D500 and a D7200 and I like both of them. I have 3 full frame cameras, all Canon.
My first was the 6D which I got because of its low light capability. It's amazing how many places allow cameras but no flash. My second I never intended to buy, the 5DSr. A friend who also works in a camera store convinced me to try one and after seeing what that camera can do I was hooked. Ironically I didn't buy it from my friend, bought it from another state and saved on the 6 percent PA sales tax. Thing about full frame is, you get use to it and the 5DSr is more of a specialty camera than an every day shooter. My daughter kept borrowing my 6D and I didn't want to use the 5DSr all the time; its image files are huge, and Canon introduced a new version of the 24-105 f/4 lens, which I wanted, which also happened to be the kit lens to the new 5D mk IV. If I got the kit I'd get the lens I wanted for half price so I bought it. To make a short story longer, my two daily shooter cameras are the Canon 5DIV and my Nikon D7200. I'm not suggesting you go Canon for your full frame camera, you'd have to buy a whole bunch of new lenses. What I'm getting at is, get the full frame camera you want, and can afford and handle. I know about schleroderma, a rare form of it, esophageal schleroderma is what brought my mother's life to an end at 85. I did extensive reading on the disease so I know how it can effect ones hands. Best of luck with which ever camera you choose and enjoy.