Need help with putting dual din in a 1984
 

I recently bought a 1984 Mercury Grand Marquis 2 dr base model with 16,350 miles.

Being that it's in pristine condition ( it was in a heated garage every day until I bought it a week ago for its entire life ) I don't want to completely tear up the dash.
Do to this, I took the panel out of my 85 that was wrecked and would like to use that to modify for a new double din.

The problem is, I've never modified anything to do this. Originally my plan was to do a single din with a screen that came out but I've realized those have completely fallen off the map and no one does that.
What I'd light is Navigation, bluetooth, and the ability to use a backup camera.

So what do I need to know, or how should I go about doing it? I have plenty of time TO do it, I just don't know how, don't know what needs to be modified in dash or how to properly mod the panel itself.