In working on my cab the solder joint on the cab seam has failed. Partly due to an accident and rust. See the pictures. The was I see it I can blast of the rust and 1. re solder it ( I have never done this) 2. use body filler 3. cut it out and weld in a patch panel. Any suggestions?
See the pictures.

https://picasaweb.google.com/106094054066011607454/CabSeam#