The rust around your window trim will be worse than it looks,,just wait until you take the trim off,,you will find hole's ( you will have to either weld up the hole's or cut the bad metal out and replace it.)
Metal is porus, like a sponge,,so wherever you see the rust,,you can count on it migrating a bit to where you can't see.

The process of rust repair and body work can vary,,depends on what kind of a job you wanna do, Fair, Good, Excellent. etc.
You will probably need a welding unit, gas or mig,,and some body work tools.
You need to post some pic's for the guy's here,,so's we can all see the extent of the damage and then we'll go from there.