nice mate. A rust section that size easyly fixed as long as its clean around the hole and not rusty. Simply put a piece of copper. (aluminium) works as well under it and weld with a mig over the top. the copper or aluminium wont weld on and can come off easy then just grind it back. Unless your looking to have the car painted on the inside for show just do it yourself with presure pack ( can get them mixed to match the color) primer is better then just paint over the top of bare metal. spray a small section first if spraying over paint because it might flair up. where there is paint use a red scotch pad to ruff it up to make the paint bond.