[oem4me]

The simple answer here is not to repaint. Save your money and polish out the original paint. Even thin factory paint is more attractive in most cases than a cheap re-do.
If the body is straight and paint is only oxidized, then by all means it should clean up well. Light surface rust can also be addressed with mild acids, leaving the underlying paint intact. This takes patience and practice, but is totally do-able and NOT expensive. Way, way less cost than even budget paint, AND you end up with a decent looking truck still wearing original paint, which means your truck is worth more.
So, instead or paying for paint and labor, invest in some good polishing equipment and professional compounds. The garbage sold at any of the chain stores is a waste of time and money compared to what the pros use, trust me.
Again, if your truck is straight and the paint is all there, DO NOT repaint.
If and when you replace the fender, paint it to match AFTER you've polished out the rest of the truck. Your color will change dramatically as you progress with the polishing.