If it were me and I REALLY wanted to fix this car, i could because i have done numerous frame off restorations and am a pretty good fabricator with a reasonably well equipped shop.
For starters, I would completely remove the interior, glass, drivetrain, etc and blow it apart. Then, I would have the body stripped to bare metal because there is no telling what you are going to find underneath the paint, in addition to what you can already see. You can tell the car has spent time in the salt already, so you know there is more.
After that, you begin the long, tedious process of cutting out and replacing all the rusty metal. Should you find the rockers are not solid and/or repairable, that is another big can of worms you will have to attack because they must be replaced in a way that ensures the door gaps don't change.
This is just part of what has to be done. If you've already lost your appetite, you should find a more solid example to learn on. Restoring a car like this is an expensive proposition even when you do most of the work yourself because if you make the body nice, now you have to do the chrome, rubber, trim, interior, glass, etc, etc. The list is long and the prices add up.
If you REALLY want to do this and you really don't care that you could have bought a nice car for the same or less, go for it. Personally, it's entertainment for me and i enjoy doing a ground up build occasionally. Otherwise, find you a nice car, spruce it up a little and drive it. (I did this with my 65 Riviera and my 61 LeSabre bubble top.) Your choice.