Hello Rockhoundrob!
Welcome!
I am new here myself. I actually joined back in 2018 when we got a used 2011 Nissan Rogue SL. But just now getting caught up on figuring out how to take care of this thing! LOL.
1) One of the things I'd suggest is to consider changing the transmission fluid.
But don't do what I did. LOL.
When I got my car, my mechanic friend told me to go get it changed. He said Nissan said the transmission fluid was good for longer than what most considered it good for. So a lot of transmissions out there are running on old, ineffective transmission fluid.
So I went and got it changed.
And then when I came here, some users were saying that your really need to go to the dealership to get the exact transmission fluid for this Rogue.
Consider reading through some of the posts below about transmission fluid change.
Heck. I would say have all the fluids checked or changed.
As for your putting the key in, I personally am not experienced enough to know what is happening.
But as far as rust underneath . . . I don't know if you can get rid of the rust. That sounds like a big project.
When we got our Rogue, it was already 7 years old . . . and came along with 7 years of rust underneath.
What I did was take it to a place to be sprayed with Corrosion Free rust protection. Basically it is a liquid that seeps into all the cracks and joints and tries to reduce the amount of water / salt touching the metal work. If you reduce the water and salt, you slow down rusting.
The application is supposed to last 18 months. So it is supposed to work out a bit cheaper than Krown. I have my minivan sprayed with Krown rust protection every year since we got it. We got it used, but only 1 year old so very minimal rust underneath. Our van is now 5 years old, and since I had it spread every year . . . if you look underneath, it looks like a 1 year old car. Very minimal rust underneath. Probably close to being only the rust that was there when we got it.
As far as Corrosion Free, talk to me in 5 years and I'll say whether I am happy with it. But . . . so far, about a year and a half into Corrosion Free, I have to say it looks like it is working well.
Oh, yeah . . . with Krown . . . you can buy aerosol cans of Krown to either apply yourself or to touch up your car in between applications.
Corrosion Free, I know I can just go to our local Canadian Tire and buy an aerosol can of it. I've used that on my lawnmower myself. And now that I've gotten our Rogue sprayed with Corrosion Free, I am using it on our Rogue.
Another, oh, yeah . . . Haynes & Chilton has repair manuals available . . .But this site has service manuals as well here . . .
https://www.nicoclub.com/nissan-service-manuals
Take care!
TheRogue