To do it right,
The rust needsz to be cut out and a patch needs to be welded in and metal finished.
Aside from the metal work it will need a slight skim of body filler
A coat or 2 of primer,
Sum wet sanding
And the area will need to be painted
You will need to blend the color into the surrounding area and re clear the entire area
It is at the back of your bed, behind the rear wheel below the body line correct?
You can get away with blending the base coat and clear up to that body line so you don't have a visible paint edge.
Its conna cost you a couple hundred bucks to repair the rust, bodywork and re paint that section
Unless they do it cheap and don't cuto out the rust holes and just fill it with fiberglass and bondo.
I've seen some nasty shit b4.
Take it to a bodyshop and ask 4 an estimate. Most collision centers give free estimates.