If you can get a three year warrenty on rust repair, go for it if the price is reasonable. Most places won't give any kind of warrenty on rust repair. I heard for aircrafts they have some kind of process that is very good at stopping rust, I imagine the regulations on aircraft are pretty strict. I can't remember what the stuff was called that they used. Rust is always fighting to come back, you can cut it out, treat the backside of the repair, and epoxy the metal and still there is a possibility it will come back, which is why most places won't offer any warrenty. The best bet is replacing the whole panel.