Well, first thought is that we can simply ignore most of the digital menu selections, and just use the defaults. I have a D800, and I'm still not completely sure what some of the menus do. But they do nothing if I leave them alone.
What happens is with time, we learn more and more about them. So you just start with a few basic menus, and ignore the rest for awhile.
Film and digital are simply different. We could buy different kinds of film for different results, but digital instead has the ISO and White Balance and Picture Control menus. Which model won't matter.
Digital has to be concerned with the memory card and buffer, and computer files and editors.
The really big difference is the processing. Unless you are already scanning film to convert to digital, digital is a really big difference. Not hard at all, in fact everything becomes easy, even the previously impossible becomes easy, but an image file is very different from a negative. The tools and options become computer operations.
I'm an old guy, but a retired programmer, and very familiar with computers. But most of my friends of my age can hardly tell a keyboard from a mouse. Some can do email and web browsing (as long as everything works), but anything new is always a big total mystery. They have digital compact cameras or phones, but all they can do is take the memory card in to be printed. They miss out on all that digital can offer in the computer. I guess I am trying to say if you are seriously comfortable with the computer, that will really help digital camera experiences.
The full frame FX cameras get expensive (and a few good FX lenses add tremendously to the cost). DX does a really fine job too, the major difference is that our lenses seem longer on DX. I was thinking (for low entry costs to get feet wet) of suggesting finding a cheap used older DX body. But that pains me, because the new bodies are tremendously improved, I think they've about got it now.
Lenses need to be at least AI compatible for any digital model.
One thing to know about the low end D3300, D5500, and some of the older low end models like D40, is that
they need AF-S lenses. Probably most of your older lenses are not AF-S, which means they will not auto focus on the D3300, d5500 series. But any old AF lens should auto focus on like D7200 or D750.
But you may want to know that the Nikon manuals are at
Nikon Product Manuals available for download | Nikon Knowledgebase
The manuals are computer searchable, and search for the section Compatible Lenses
You will need a new iTTL flash too.
