1997 Ford F-150 Door Panel rust and repair

I have rust on the 3rd door of my extended cab. It seemes to be extensive (im a little new to this stuff so im not too sure) I will post pictures along with this to show what im talking about.
My question is what should i use to repair this. Shou;d i use bondo or should i cut it out and weld new sheet metal in and re paint? The rust goes through the bottom of the door, I got at the door with a wire wheel and it went through the door, not sure if thats whats gonna happen with the rest